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A local anesthetic (LA) is a
medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, therapy, treat, or preventive medicine, prevent disease. Drug therapy (pharmacotherapy) ...

medication
that causes absence of
pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain The International Association for the Study of Pain (IASP) is an international learned society A learned societ ...
sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciousness, as opposed to a
general anesthetic General anaesthetics (or anesthetics, see spelling differences Despite the various English dialects Dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from , , "through" and , , "I speak") is used in ...
. When it is used on specific nerve pathways (
local anesthetic nerve block Local anesthetic nerve block (local anesthetic regional nerve blockade, or often simply nerve block) is a short-term nerve block involving the injection (medicine), injection of local anesthetic as close to the nerve as possible for analgesia, pai ...
),
paralysis Paralysis (also known as plegia) is a loss of motor function in one or more muscle Muscle is a soft tissue found in most animals. Muscle cells contain protein Proteins are large biomolecules or macromolecules that are comprised of ...
(loss of
muscle Skeletal muscles (commonly referred to as muscles) are organs An organ is a group of tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tissues can be broadly cat ...

muscle
power) also can be achieved.


Examples

Short Duration & Low Potency
Procaine Procaine is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciou ...

Procaine
Chloroprocaine Chloroprocaine (trade name Nesacaine, Nesacaine-MPF) (often in the hydrochloride salt form as the aforementioned trade names) is a local anesthetic given by Injection (medicine), injection during surgery, surgical procedures and childbirth, labor an ...

Chloroprocaine
Medium Duration & Potency
Lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates ...

Lidocaine
Prilocaine Prilocaine () is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consc ...

Prilocaine
High Duration & Potency
Tetracaine Tetracaine, also known as amethocaine, is an ester local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of ...

Tetracaine
Bupivacaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

Bupivacaine
Cinchocaine Cinchocaine (International Nonproprietary Name, INN/British Approved Name, BAN) or dibucaine (United States Adopted Name, USAN) is an amide local anesthetic. Among the most potent and toxic of the long-acting local anesthetics, current use of cincho ...

Cinchocaine
Ropivacaine Ropivacaine ( rINN) is a local anaesthetic drug belonging to the amino amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula RC(=O)NR′R″, where R, R', and R″ re ...

Ropivacaine
Clinical LAs belong to one of two classes: aminoamide and aminoester local anesthetics. Synthetic LAs are structurally related to
cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

cocaine
. They differ from cocaine mainly in that they have a very low abuse potential and do not produce
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a Chronic condition, long-term Disease, medical condition in which the blood pressure in the artery, arteries is persistently elevated. High blood pressure usually does not ...

hypertension
or (with few exceptions)
vasoconstriction Vasoconstriction is the narrowing of the blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of th ...

vasoconstriction
. They are used in various techniques of
local anesthesia Local anesthesia is any technique to induce the absence of sensationSensation refers to the processing of sense Sense relates to any of the systems and corresponding organs involved in sensation, i.e. the physical process of responding to Stimulu ...
such as: *
Topical anesthesiaA topical anesthetic is a local anesthetic that is used to numb the surface of a body part. They can be used to numb any area of the human skin, skin as well as the front of the human eyeball, eyeball, the inside of the Human nose, nose, ear or throa ...
(surface) * Topical administration of cream, gel, ointment, liquid, or spray of anaesthetic dissolved in
DMSO Dimethyl sulfoxide (DMSO) is an organosulfur compound Organosulfur compounds are organic compound , CH4; is among the simplest organic compounds. In chemistry Chemistry is the scientific discipline involved with Chemical element, elements ...

DMSO
or other solvents/carriers for deeper absorption *
Infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (med ...
*
Brachial plexus block Brachial plexus block is a regional anesthesia technique that is sometimes employed as an alternative or as an adjunct to general anesthesia General anaesthesia or general anesthesia (see American and British English spelling differences, spellin ...
* Epidural (extradural) block *
Spinal anesthesia Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic or opioid into the subar ...

Spinal anesthesia
(subarachnoid block) *
Iontophoresis Iontophoresis is a process of transdermal drug delivery by use of a voltage gradient on the skin. Molecules are transported across the stratum corneum by electrophoresis and electroosmosis and the electric field can also increase the permeability of ...

Iontophoresis
The suffix "-caine" at the ends of these medication names was extracted from the word "
cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

cocaine
", because cocaine was formerly used as a local anesthetic.


Medical uses


Acute pain

Acute pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain The International Association for the Study of Pain (IASP) is an international learned society A learned society ...
may occur due to trauma, surgery, infection, disruption of blood circulation, or many other conditions in which tissue injury occurs. In a medical setting, pain alleviation is desired when its warning function is no longer needed. Besides improving patient comfort, pain therapy can also reduce harmful physiological consequences of untreated pain. Acute pain can often be managed using
analgesic An analgesic or painkiller is any member of the group of Pharmaceutical drug, drugs used to achieve analgesia, relief from pain. They are distinct from anesthetics, which temporarily affect, and in some instances completely eliminate, sense, sens ...
s. However, conduction anesthesia may be preferable because of superior pain control and fewer side effects. For purposes of pain therapy, LA drugs are often given by repeated injection or continuous infusion through a catheter. LA drugs are also often combined with other agents such as opioids for synergistic analgesic action. Low doses of LA drugs can be sufficient so that muscle weakness does not occur and patients may be mobilized. Some typical uses of conduction anesthesia for acute pain are: * Labor pain (epidural anesthesia, pudendal nerve blocks) * Postoperative pain (peripheral nerve blocks, epidural anesthesia) * Trauma (peripheral nerve blocks, intravenous regional anesthesia, epidural anesthesia)


Chronic pain

Chronic pain Chronic pain is classified as pain that lasts longer than three to six months. In medicine, the distinction between Acute (medicine), acute and Chronic condition, chronic pain is sometimes determined by the amount of time since onset. Two commonly ...
is a complex and often serious condition that requires diagnosis and treatment by an expert in pain medicine. LAs can be applied repeatedly or continuously for prolonged periods to relieve chronic pain, usually in combination with medication such as
opioid Opioids are substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...
s,
NSAID Nonsteroidal anti-inflammatory drugs (NSAIDs) are members of a drug class A drug is any chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass a ...
s, and
anticonvulsant Anticonvulsants (also commonly known as antiepileptic drugs or as antiseizure drugs) are a diverse group of pharmacological Pharmacology is a branch of medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of ...
s. Though it can be easily performed, repeated local anaesthetic blocks in chronic pain conditions are not recommended as there is no evidence of long-term benefits.


Surgery

Virtually every part of the body can be anesthetized using conduction anesthesia. However, only a limited number of techniques are in common clinical use. Sometimes, conduction anesthesia is combined with
general anesthesia General anaesthesia or general anesthesia (see American and British English spelling differences, spelling differences) is a medically induced coma with loss of protective reflexes, resulting from the administration of one or more general anaest ...
or
sedation Sedation is the reduction of irritability Irritability is the excitatory ability that living organisms In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, B ...
for the patient's comfort and ease of surgery. However, many anaesthetists, surgeons, patients and nurses believe that it is safer to perform major surgeries under local anesthesia than general anesthesia. Typical operations performed under conduction anesthesia include: *
Dentistry Dentistry, also known as dental medicine and oral medicine, is a branch of medicine that consists of the study, diagnosis, prevention, and treatment of diseases, disorders, and conditions of the mouth, oral cavity (the mouth), commonly in the ...

Dentistry
(surface anesthesia, infiltration anesthesia or intraligamentary anesthesia during restorative operations such as fillings, crowns, and root canals, or extractions, and regional nerve blocks during extractions and surgeries) *
Podiatry Podiatry () or podiatric medicine () is a branch of medicine Medicine is the science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity, awareness, or understanding of someone o ...

Podiatry
(cutaneous, nail avulsions, matricectomy, bunionectomy, hammertoe repair and various other podiatric procedures) *
Eye surgery Eye surgery, also known as ocular surgery, is surgery Surgery ''cheirourgikē'' (composed of χείρ, "hand", and ἔργον, "work"), via la, chirurgiae, meaning "hand work". is a medical or dental specialty that uses operative manual an ...

Eye surgery
(surface anesthesia with
topical anesthetic A topical anesthetic is a local anesthetic A local anesthetic (LA) is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, thera ...
s or
retrobulbar block A retrobulbar block is a regional anesthetic nerve block in the retrobulbar space, the area located behind the globe of the eye. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia ...
during cataract removal or other ophthalmic procedures) * ENT operations, head and neck surgery (infiltration anesthesia, field blocks, or peripheral nerve blocks, plexus anesthesia) * Shoulder and arm surgery (plexus anesthesia or intravenous regional anesthesia) * Heart and lung surgery ( epidural anesthesia combined with general anesthesia) *
Abdominal surgery The term abdominal surgery broadly covers surgical procedures that involve opening the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in ...
(epidural anesthesia/
spinal anesthesia Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the intrathecal administration, injection of a local anaestheti ...
, often combined with general anesthesia during inguinal hernia repair or other abdominal surgery ) * Gynecological, obstetrical, and urological operations (spinal/epidural anesthesia) * Bone and joint surgery of the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen The abdomen (colloquially called the belly, tummy, midriff or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in ...

pelvis
,
hip In vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, ...

hip
, and
leg A leg is a weight-bearingIn orthopedics Orthopedic surgery or orthopedics, is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat muscul ...

leg
(spinal/epidural anesthesia, peripheral nerve blocks, or intravenous regional anesthesia) * Surgery of skin and peripheral blood vessels (
topical anesthesiaA topical anesthetic is a local anesthetic that is used to numb the surface of a body part. They can be used to numb any area of the human skin, skin as well as the front of the human eyeball, eyeball, the inside of the Human nose, nose, ear or throa ...
, field blocks, peripheral nerve blocks, or spinal/epidural anesthesia)


Diagnostic Tests

Diagnostic tests such as bone marrow aspiration, lumbar puncture (spinal tap) and aspiration of cysts or other structures are made to be less painful upon administration of local anesthetic before insertion of larger needles.


Other uses

Local anesthesia is also used during insertion of IV devices, such as pacemakers and implantable defibrillators, ports used for giving chemotherapy medications and hemodialysis access catheters. Topical anesthesia, in the form of lidocaine/prilocaine (EMLA) is most commonly used to enable relatively painless
venipuncture In medicine, venipuncture or venepuncture is the process of obtaining intravenous access for the purpose of venous blood sampling (also called ''phlebotomy Phlebotomy is the process of making a puncture in a vein Veins are blood vessels tha ...
(
blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers t ...

blood
collection) and placement of intravenous cannulae. It may also be suitable for other kinds of punctures such as
ascites Ascites is the abnormal build-up of fluid in the abdomen. Technically, it is more than 25 ml of fluid in the peritoneal cavity, although volumes greater than one liter may occur. Symptoms may include increased abdominal size, increased weight, abd ...
drainage and
amniocentesis Amniocentesis (also referred to as an amniotic fluid test or, informally, an "amnio") is a medical procedureThe word ''amniocentesis'' itself indicates precisely the procedure in question, Ancient Greek, Greek ἀμνίον ''amníon'' being the "i ...

amniocentesis
. Surface anesthesia also facilitates some
endoscopic An endoscopy (''looking inside'') is a procedure used in medicine Medicine is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), ...

endoscopic
procedures such as
bronchoscopy Bronchoscopy is an endoscopic medical procedure, technique of visualizing the inside of the airways for diagnostic and therapeutic purposes. An instrument (bronchoscope) is inserted into the airways, usually through the nose or mouth, or occasiona ...

bronchoscopy
(visualization of the lower airways) or
cystoscopy Cystoscopy is endoscopy An endoscopy (''looking inside'') is a procedure used in medicine Medicine is the Art (skill), art, science, and Praxis (process) , practice of caring for a patient and managing the diagnosis, prognosis, Preventive me ...
(visualization of the inner surface of the bladder)


Side effects


Localized side effects

Edema of tongue, pharynx and larynx may develop as a side effect of local anaesthesia. This could be caused by a variety of reasons including trauma during injection, infection, an allergic reaction, haematoma or injection of irritating solutions such as cold-sterilisation solutions. Usually there is tissue swelling at the point of injection. This is due to puncturing of the vein which allows the blood to flow into loose tissues in the surrounding area. Blanching of the tissues in the area where the local anaesthetic is deposited is also common. This gives the area a white appearance as the blood flow is prevented due to vasoconstriction of arteries in the area. The vasoconstriction stimulus gradually wears off and subsequently the tissue returns to normal in less than 2 hours. The side effects of inferior alveolar nerve block include feeling tense, clenching of the fists and moaning. The duration of soft tissue anaesthesia is longer than pulpal anaesthesia and is often associated with difficulty eating, drinking and speaking.


Risks

The risk of temporary or permanent nerve damage varies between different locations and types of
nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block Local anesthetic nerve block (local anesthetic regional nerve blockade, o ...
s. There is risk of accidental damage to local blood vessels during injection of the local anaesthetic solution. This is referred to as Haematoma and could result in pain, trismus, swelling and/or discolouration of the region. The density of tissues surrounding the injured vessels is an important factor for Haematoma. There is greatest chance of this occurring in a posterior superior alveolar nerve block or in a pterygomandibular block. Giving local anaesthesia to patients with liver disease can have significant consequences. Thorough evaluation of the disease should be carried out to assess potential risk to the patient as in significant liver dysfunction, the half-life of amide local anaesthetic agents may be drastically increased thus increasing the risk of overdose. Local anaesthetics and vasoconstrictors may be administered to pregnant patients however it is very important to be extra cautious when giving a pregnant patient any type of drug. Lidocaine can be safely used but bupivacaine and mepivacaine should be avoided.  Consultation with the obstetrician is vital before administrating any type of local anaesthetic to a pregnant patient.


Recovery

Permanent nerve damage after a peripheral nerve block is rare. Symptoms are likely to resolve within a few weeks. The vast majority of those affected (92%–97%) recover within four to six weeks; 99% of these people have recovered within a year. An estimated one in 5,000 to 30,000 nerve blocks results in some degree of permanent persistent nerve damage. Symptoms may continue to improve for up to 18 months following injury.


Potential side effects

General systemic adverse effects are due to the pharmacological effects of the anesthetic agents used. The conduction of electric impulses follows a similar mechanism in
peripheral nerves The peripheral nervous system (PNS) is one of two components that make up the nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sen ...
, the
central nervous system The central nervous system (CNS) is the part of the nervous system In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecu ...

central nervous system
, and the
heart The heart is a muscular MUSCULAR (DS-200B), located in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' and Telegraph' use ...

heart
. The effects of local anesthetics are, therefore, not specific for the signal conduction in peripheral nerves. Side effects on the central nervous system and the heart may be severe and potentially fatal. However, toxicity usually occurs only at plasma levels which are rarely reached if proper anesthetic techniques are adhered to. High plasma levels might arise, for example, when doses intended for
epidural Epidural administration (from Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the foll ...
or intrasupport tissue administration are accidentally delivered as
intravascular The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...
injection.


Emotional reactions

When patients are emotionally affected in the form of nervousness or fear, it can lead to vasovagal collapse. This is the anticipation of pain during administration that activates the
parasympathetic nervous system The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system The autonomic nervous system (ANS), formerly the vegetative nervous system, is a division of the peripheral nervous system that supplies s ...
while inhibiting the orthosympathetic nervous system. What results is a dilation of arteries in muscles which can lead to a reduction in circulating blood volume inducing a temporary shortness of blood flow to the brain. Notable symptoms include restlessness, visibly looking pale, perspiration and possible the loss of consciousness. In severe cases, clonic cramps resembling an epileptic insult may occur. On the other hand, fear of administration can also result in accelerated, shallow breathing, or
hyperventilation Hyperventilation occurs when the rate or tidal volume Tidal volume (symbol VT or TV) is the volume of air moved into or out of the lungs during a normal breath. In a healthy, young human adult, tidal volume is approximately 500 ml per i ...
. The patient may feel a tingling sensation in hands and feet or a sense of light-headedness and increased chest pressure. Hence, it is crucial for the medical professional administrating the local anaesthesia, especially in the form of an injection, to ensure that the patient is in a comfortable setting and has any potential fears alleviated in order to avoid these possible complications.


Central nervous system

Depending on local tissue concentrations of local anesthetics, excitatory or depressant effects on the central nervous system may occur. Initial symptoms of systemic toxicity include ringing in the ears (
tinnitus Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone will experience a faint "normal tinnitus" in a completely quiet room but it is only of concern if it is bothersome or interferes with normal h ...

tinnitus
), a metallic taste in the mouth, tingling or numbness of the mouth, dizziness and/or disorientation. At higher concentrations, a relatively selective depression of inhibitory neurons results in cerebral excitation, which may lead to more advanced symptoms include motor twitching in the periphery followed by grand mal seizures. It is reported that seizures are more likely to occur when bupivacaine is used, particularly in combination with chloroprocaine. A profound depression of brain functions may occur at even higher concentrations which may lead to
coma A coma is a deep state of prolonged unconsciousness Unconsciousness is a state which occurs when the ability to maintain an consciousness, awareness of self and environment is lost. It involves a complete, or near-complete, lack of responsive ...
,
respiratory arrest Respiratory arrest is caused by apnea Apnea (BrE British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification ...
, and death. Such tissue concentrations may be due to very high plasma levels after intravenous injection of a large dose. Another possibility is direct exposure of the central nervous system through the
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochor ...
, i.e., overdose in spinal anesthesia or accidental injection into the subarachnoid space in epidural anesthesia.


Cardiovascular system

Cardiac toxicity can result from improper injection of agent into a vessel. Even with proper administration, it is inevitable for some diffusion of agent into the body from the site of application due to unforeseeable anatomical idiosyncrasies of the patient. This may affect the nervous system or cause the agent to enter into general circulation. However, infections are very seldom transmitted. Cardiac toxicity associated with overdose of intravascular injection of local anesthetic is characterized by
hypotension Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the Systole, systolic blood pressure (the top number) and ...
, atrioventricular conduction delay, idioventricular rhythms, and eventual cardiovascular collapse. Although all local anesthetics potentially shorten the myocardial refractory period,
bupivacaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

bupivacaine
blocks the cardiac sodium channels, thereby making it most likely to precipitate malignant
arrhythmias Arrhythmia, also known as cardiac arrhythmia or heart arrhythmia, is a group of conditions in which the heartbeat Heartbeat or heartbeats may refer to: Physiology *Cardiac cycle, of the heart *Contraction of the cardiac muscle, muscles of the ...
. Even and
ropivacaine Ropivacaine ( rINN) is a local anaesthetic drug belonging to the amino amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula RC(=O)NR′R″, where R, R', and R″ re ...

ropivacaine
(single-enantiomer derivatives), developed to ameliorate cardiovascular side effects, still harbor the potential to disrupt cardiac function. Toxicity from anesthetic combinations is additive.


Endocrine

Endocrine and metabolic systems only have slightly adverse effects with most cases being without clinical repercussions.


Immunologic allergy

Adverse reactions to local anesthetics (especially the esters) are not uncommon, but legitimate
allergies Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity Hypersensitivity (also called hypersensitivity reaction or intolerance) refers to undesirable reactions produced by the normal immune system, ...

allergies
are very rare. Allergic reactions to the esters is usually due to a sensitivity to their metabolite,
para-aminobenzoic acid 4-Aminobenzoic acid (also known as ''para''-aminobenzoic acid or PABA because the number 4 carbon in the benzene ring Benzene is an organic chemical compound A chemical compound is a chemical substance composed of many identical molecule ...

para-aminobenzoic acid
, and does not result in cross-allergy to amides.Univ. of Wisconsin, Local Anesthesia and Regional Anesthetics Therefore, amides can be used as alternatives in those patients. Nonallergic reactions may resemble allergy in their manifestations. In some cases, skin tests and provocative challenge may be necessary to establish a diagnosis of allergy. Also cases of allergy to
paraben Parabens are a class of widely used preservatives A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs, paints, biological samples, cosmetics, wood, and many other produc ...
derivatives occur, which are often added as preservatives to local anesthetic solutions.


Methemoglobinemia

Methemoglobinemia Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications may ...
is a process where iron in hemoglobin is altered, reducing its oxygen-carrying capability, which produces
cyanosis Cyanosis is the change of body Tissue (biology), tissue color to a bluish-purple hue as a result of having decreased amounts of oxygen bound to the hemoglobin in the Red blood cell, red blood cells of the capillary bed. Body tissues that reflect ...
and symptoms of hypoxia. Exposure to aniline group chemicals such as
benzocaine Benzocaine, sold under the brand name Orajel amongst others, is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a and ...

benzocaine
,
lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic A local anesthetic (LA) is a medication A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug o ...

lidocaine
, and
prilocaine Prilocaine () is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consc ...

prilocaine
can produce this effect, especially benzocaine. The systemic toxicity of prilocaine is comparatively low, but its metabolite, o-toluidine, is known to cause
methemoglobinemia Methemoglobinemia, or methaemoglobinaemia, is a condition of elevated methemoglobin in the blood. Symptoms may include headache, dizziness, shortness of breath, nausea, poor muscle coordination, and blue-colored skin (cyanosis). Complications may ...
.


Second-generation effects

Application of local anesthetics during oocyte removal during in vitro fertilisation has been up to debate. Pharmacological concentrations of anesthetic agents have been found in follicular fluid. Clinical trials have not concluded any effects on pregnant women. However, there is some concern with the behavioral effects of lidocaine on offspring in rats. During pregnancy, it is not common for local anesthetics to have any adverse effect on the fetus. Despite this, risks of toxicity may be higher in pregnancy due to an increase in unbound fraction of local anesthetic and physiological changes increase the transfer of local anesthetic into the central nervous system. Hence, it is recommended that pregnant women use a lower dose of local anesthetic to reduce any potential complications.


Treatment of overdose: "Lipid rescue"

This method of toxicity treatment was invented by Dr. Guy Weinberg in 1998, and was not widely used until after the first published successful rescue in 2006. Evidence indicates Intralipid, a commonly available intravenous lipid emulsion, can be effective in treating severe cardiotoxicity secondary to local anesthetic overdose, including human case reports of successful use in this way ( lipid rescue). However, the evidence at this point is still limited. Though most reports to date have used Intralipid, a commonly available intravenous lipid emulsion, other emulsions, such as Liposyn and Medialipid, have also been shown effective. Ample supporting animal evidence and human case reports show successful use in this way. In the UK, efforts have been made to publicise this use more widely and lipid rescue has now been officially promoted as a treatment by the
Association of Anaesthetists of Great Britain and Ireland The Association of Anaesthetists, in full the Association of Anaesthetists of Great Britain and Ireland (AAGBI), is a professional association for anaesthesiology, anaesthetists in the United Kingdom and Republic of Ireland, Ireland. It was fou ...
. One published case has been reported of successful treatment of refractory
cardiac arrest Cardiac arrest is a sudden loss of blood flow Hemodynamics American and British English spelling differences#ae and oe, or haemodynamics are the Fluid dynamics, dynamics of blood flow. The circulatory system is controlled by homeostasis, homeost ...
in
bupropion Bupropion, sold under the brand names Wellbutrin and Zyban among others, is a medication primarily used to treat major depressive disorder and to support smoking cessation. It is an effective antidepressant on its own, but it is also used as ...

bupropion
and
lamotrigine Lamotrigine, sold as the brand name Lamictal among others, is a medication used to treat epilepsy Epilepsy is a group of non-communicable neurological disorder A neurological disorder is any disorder of the nervous system In Biolog ...

lamotrigine
overdose using lipid emulsion. The design of a 'homemade' lipid rescue kit has been described. Although lipid rescue mechanism of action is not completely understood, the added lipid in the blood stream may act as a sink, allowing for the removal of lipophilic toxins from affected tissues. This theory is compatible with two studies on lipid rescue for clomipramine toxicity in rabbits and with a clinical report on the use of lipid rescue in veterinary medicine to treat a puppy with toxicosis.


Mechanism of action

All LAs are
membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecule A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A m ...
-stabilizing drugs; they reversibly decrease the rate of depolarization and repolarization of excitable membranes (like
nociceptors A nociceptor ("pain receptor") is a sensory neuron Sensory neurons, also known as afferent neurons, are neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called ...
). Though many other drugs also have membrane-stabilizing properties, not all are used as LAs (
propranolol Propranolol, sold under the brand name Inderal among others, is a medication of the beta blocker Beta blockers (beta-blockers, β-blockers, etc.) are a class of medications that are predominantly used to manage abnormal heart rhythms, and ...

propranolol
, for example, though it has LA properties). LA drugs act mainly by inhibiting
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
influx through sodium-specific
ion channel Ion channels are pore-forming membrane protein Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. Integral membrane ...

ion channel
s in the
neuron A neuron or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapse In the nervous system In biology Biology is the natural science that studies life and living ...

neuron
al
cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...

cell membrane
, in particular the so-called voltage-gated sodium channels. When the influx of sodium is interrupted, an
action potential In physiology Physiology (; ) is the scientific Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence ...

action potential
cannot arise and signal conduction is inhibited. The receptor site is thought to be located at the cytoplasmic (inner) portion of the sodium channel. Local anesthetic drugs bind more readily to sodium channels in an activated state, thus onset of neuronal blockade is faster in rapidly firing neurons. This is referred to as state-dependent blockade. LAs are weak bases and are usually formulated as the hydrochloride salt to render them water-soluble. At a pH equal to the protonated base's pKa, the protonated (ionized) and unprotonated (unionized) forms of the molecule exist in equimolar amounts, but only the unprotonated base diffuses readily across cell membranes. Once inside the cell, the local anesthetic will be in equilibrium, with the formation of the protonated (ionized) form, which does not readily pass back out of the cell. This is referred to as "ion-trapping". In the protonated form, the molecule binds to the LA binding site on the inside of the ion channel near the cytoplasmic end. Most LAs work on the internal surface of the membrane - the drug has to penetrate the cell membrane, which is achieved best in the nonionised form. This is exemplified by the permanently ionised LA which cannot
diffuse 250px, Diffusion from a microscopic and macroscopic point of view. Initially, there are solution, solute molecules on the left side of a barrier (purple line) and none on the right. The barrier is removed, and the solute diffuses to fill the wh ...

diffuse
across the cell membrane but, if injected into the cytosol of a nerve fibre, can induce NaKATPase blockage and anaesthetic effects. Acidosis such as caused by inflammation at a wound partly reduces the action of LAs. This is partly because most of the anesthetic is ionized and therefore unable to cross the cell membrane to reach its cytoplasmic-facing site of action on the sodium channel. All nerve fibers are sensitive to LAs, but due to a combination of diameter and myelination, fibers have different sensitivities to LA blockade, termed differential blockade. Type B fibers (sympathetic tone) are the most sensitive followed by type C (pain), type A delta (temperature), type A gamma (proprioception), type A beta (sensory touch and pressure), and type A alpha (motor). Although type B fibers are thicker than type C fibers, they are myelinated, thus are blocked before the unmyelinated, thin C fiber.


Techniques

Local anesthetics can block almost every nerve between the peripheral nerve endings and the central nervous system. The most peripheral technique is topical anesthesia to the skin or other body surface. Small and large peripheral nerves can be anesthetized individually (peripheral nerve block) or in anatomic nerve bundles (plexus anesthesia). Spinal anesthesia and epidural anesthesia merge into the central nervous system. Injection of LAs is often painful. A number of methods can be used to decrease this pain, including buffering of the solution with bicarbonate and warming. Clinical techniques include: * Surface anesthesia is the application of an LA spray, solution, or cream to the skin or a mucous membrane; the effect is short lasting and is limited to the area of contact. * Infiltration anesthesia is
infiltration Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (med ...

infiltration
of LA into the tissue to be anesthetized; surface and infiltration anesthesia are collectively topical anesthesia * Field block is subcutaneous injection of an LA in an area bordering on the field to be anesthetized. *
Peripheral nerve block Nerve block or regional nerve blockade is any deliberate interruption of signals traveling along a nerve, often for the purpose of pain relief. Local anesthetic nerve block (sometimes referred to as simply "nerve block") is a short-term block, usu ...
is injection of LA in the vicinity of a peripheral nerve to anesthetize that nerve's area of innervation. * Plexus anesthesia is injection of LA in the vicinity of a
nerve plexus A nerve plexus is a plexus (branching network) of intersecting nerves. A nerve plexus is composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels. There are five spinal nerve plex ...
, often inside a tissue compartment that limits the diffusion of the drug away from the intended site of action. The anesthetic effect extends to the innervation areas of several or all nerves stemming from the plexus. * Epidural anesthesia is an LA injected into the
epidural space In anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science which deals with the structural organization of liv ...
, where it acts primarily on the
spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

spinal nerve
roots; depending on the site of injection and the volume injected, the anesthetized area varies from limited areas of the abdomen or chest to large regions of the body. * Spinal anesthesia is an LA injected into the
cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochor ...
, usually at the lumbar spine (in the lower back), where it acts on
spinal nerve A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the ...

spinal nerve
roots and part of the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column. It encloses the central canal of the spinal cord, which contain ...

spinal cord
; the resulting anesthesia usually extends from the legs to the abdomen or chest. * Intravenous regional anesthesia (Bier's block) is when blood circulation of a limb is interrupted using a tourniquet (a device similar to a blood-pressure cuff), then a large volume of LA is injected into a peripheral vein. The drug fills the limb's venous system and diffuses into tissues, where peripheral nerves and nerve endings are anesthetized. The anesthetic effect is limited to the area that is excluded from blood circulation and resolves quickly once circulation is restored. * Local anesthesia of body cavities includes intrapleural anesthesia and intra-articular anesthesia. * Transincision (or transwound) catheter anesthesia uses a multilumen catheter inserted through an incision or wound and aligned across it on the inside as the incision or wound is closed, providing continuous administration of local anesthetic along the incision or wounds Dental-specific techniques include:


Vazirani-Alkinosi Technique

The Vazirani-alkinosi technique is also known as the closed-mouth mandibular nerve block. It is mostly used in patients who have limited opening of the mandible or in those that have trismus; spasm of the muscles of mastication. The nerves which are anesthetised in this technique are the inferior alveolar, incisive, mental, lingual and mylohyoid nerves. Dental needles are available in 2 lengths; short and long. As Vazirani-akinosi is a local anaesthetic technique which requires penetration of a significant thickness of soft tissues, a long needle is used. The needle is inserted into the soft tissue which covers the medial border of the mandibular ramus, in region of the inferior alveolar, lingual and mylohyoid nerves. The positioning of the bevel of the needle is very important as it must be positioned away from the bone of the mandibular ramus and instead towards the midline.


Intraligamentary Infiltration

Intraligamentary infiltration, also known as periodontal ligament injection or intraligamentary injection (ILIs), is known as “the most universal of the supplemental injections”. ILIs are usually administered when inferior alveolar nerve block techniques are inadequate or ineffective. ILIs are purposed for: 1. Single-tooth anesthesia 2. Low anesthetic dose 3. Contraindication for systemic anesthesia 4. Presence of systemic health problems ILI utilization is expected to increase because dental patients prefer fewer soft tissue anesthesia and dentists aim to reduce administration of traditional inferior alveolar nerve block (INAB) for routine restorative procedures. Injection methodology: The periodontal ligament space provides an accessible route to the cancellous alveolar bone, and the anesthetic reaches the pulpal nerve via natural perforation of intraoral bone tissue. Advantages of ILI over INAB: rapid onset (within 30 seconds), small dosage required (0.2-1.0mL), limited area of numbness, lower intrinsic risks such as neuropathy, hematoma, trismus/jaw sprain and self-inflicted periodontal tissue injury, as well as decreased cardiovascular disturbances. Its usage as a secondary or supplementary anesthesia on the mandible has reported a high success rate of above 90%. Disadvantages: Risk of temporary periodontal tissue damage, likelihood of bacteriemia and endocarditis for at-risk populations, appropriate pressure and correct needle placement are imperative for anesthetic success, short duration of pulpal anesthesia limits the use of ILIs for several restorative procedures that require longer duration, postoperative discomfort, and injury on unerupted teeth such as enamel hypoplasia and defects. Technique description: * All plaque and calculus to be eradicated, optimally before the operative visit to assist gingival tissue healing. * Before injection, disinfect gingival sulcus with 0.2% chlorhexidine solution. * Administration of soft tissue anesthesia is recommended prior to ILI administration. This helps to enhance patient comfort. * Needle gauges of sizes 27-gauge short or 30-gauge ultra-short needle are usually utilized. * The needle is inserted along the long axis, at a 30-degree angle, of the mesial or distal root for single rooted teeth and on the mesial and distal roots of multi-rooted teeth. Bevel orientation toward the root provides easier advancement of the needle apically. * When the needle reaches between the root and crestal bone, significant resistance is experience. * Anesthetic deposition is recommended at 0.2mL, per root or site, over minimally 20 seconds. * For its success, the anesthetic must be administered under pressure. It must not leak out of the sulcus into the mouth. * Withdraw needle for minimally 10–15 seconds to permit complete deposition of solution. This can be slower than other injections as there is pressure build-up from the anesthetic administration. * Blanching of the tissue is observed and may be more evident when vasoconstrictors are used. It is caused by a temporary obstruction of blood flow to the tissue. Syringes: * Standard syringes can be used. * The intraligamentary syringe offers mechanical advantage by using a trigger-grasp or click apparatus to employ a gear or lever that improves control and results in increased force to push the anesthetic cartridge's rubber stopper forward for medication deposition with greater ease. * C-CLADs (computer controlled local anesthetic delivery devices) can be used. Its usage of computer microprocessors allows for control of fluid dynamics and anesthetic deposition. This minimizes subjective flow rates and variability in pressure. This thereby results in enhanced hydrodynamic diffusion of solution into bone or the target area of deposition, thus permitting larger amounts of anesthetic solution to be delivered during ILIs without increased tissue damage. Things to note: * ILIs are not recommended for patients with active periodontal inflammation. * ILIs should not be administered at tooth sites with 5mm or more of periodontal attachment loss.


Gow-Gates Technique

Gow-Gates technique is used to provide anesthetics to the mandible of the patient's mouth. With the aid of extra and intraoral landmarks, the needle is injected into the intraoral latero-anterior surface of the condyle, steering clear below the insertion of the lateral pterygoid muscle. The extraoral landmarks used for this technique are the lower border of the ear tragus, corners of the mouth and the angulation of the tragus on the side of the face. Biophysical forces (pulsation of the maxillary artery, muscular function of jaw movement) and gravity will aid with the diffusion of anesthetic to fill the whole pterygomandibular space. All three oral sensory parts of the mandibular branch of the trigeminal nerve and other sensory nerves in the region will come in contact with the anesthetic and this reduces the need to anesthetise supplementary innervation. In comparison to other regional block methods of anestheising the lower jaw, the Gow-Gates technique has a higher success rate in fully anesthetising the lower jaw. One study found that out of 1,200 patients receiving injections through the Gow-Gate technique, only 2 of them did not obtain complete anesthesia.


Types

Local anesthetic solutions for injection typically consist of: * The local anesthetic agent itself * A vehicle, which is usually water-based or just sterile water *
Vasoconstrictor Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessels ...
possibly (see below) *
Reducing agent A reducing agent (also called a reductant, reducer, or electron donor) is an element or compound that loses or "donates" an electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one ele ...
(antioxidant), e.g. if epinephrine is used, then
sodium metabisulfite Sodium metabisulfite or sodium pyrosulfite (IUPAC spelling; Br. E. sodium metabisulphite or sodium pyrosulphite) is an inorganic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the ...

sodium metabisulfite
is used as a reducing agent *
Preservative A preservative is a substance or a chemical that is added to products such as food products, beverages, pharmaceutical drugs A medication (also referred to as medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug File: ...
, e.g.
methylparaben Methylparaben, also methyl paraben, one of the parabens Image:Paraben-2D-skeletal.png, 150 px, General chemical structure of a paraben(a ''para''-hydroxybenzoate)where R = an alkyl group Parabens are a class of widely used preservatives in cosmet ...

methylparaben
*
Buffer Buffer may refer to: Science * Buffer gas, an inert or nonflammable gas * Buffer solution, a solution used to prevent changes in pH * Buffering agent, the weak acid or base in a buffer solution * Lysis buffer, in cell biology * Metal ion buffer * M ...
Esters An ester is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemic ...
are prone to producing allergic reactions, which may necessitate the use of an
amide In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

amide
. The names of each locally clinical anesthetic have the suffix "-caine". Most ester LAs are metabolized by pseudocholinesterase, while amide LAs are metabolized in the liver. This can be a factor in choosing an agent in patients with liver failure, although since cholinesterases are produced in the liver, physiologically (e.g. very young or very old individual) or pathologically (e.g.
cirrhosis Cirrhosis, also known as liver cirrhosis or hepatic cirrhosis, and end-stage liver disease, is the impaired liver function caused by the formation of scar tissue known as fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wo ...
) impaired hepatic metabolism is also a consideration when using esters. Sometimes, LAs are combined, e.g.: * Lidocaine/prilocaine (EMLA, eutectic mixture of local anesthetic) * Lidocaine/tetracaine (Rapydan) * TAC LA solutions for injection are sometimes mixed with vasoconstrictors (
combination drug A combination drug or a fixed-dose combination (FDC) is a medicine that includes two or more active ingredients combined in a single dosage form. Terms like "combination drug" or "combination drug product" can be common shorthand for a FDC produ ...
) to increase the duration of local anesthesia by constricting the blood vessels, thereby safely concentrating the anesthetic agent for an extended duration, as well as reducing
hemorrhage Bleeding, also known as a hemorrhage, haemorrhage, or simply blood loss, is blood Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the Cell (biology), cells and transports ...
. Because the vasoconstrictor temporarily reduces the rate at which the systemic circulation removes the local anesthetic from the area of the injection, the maximum doses of LAs when combined with a vasoconstrictor is higher compared to the same LA without any vasoconstrictor. Occasionally, cocaine is administered for this purpose. Examples include: *
Prilocaine Prilocaine () is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consc ...

Prilocaine
hydrochloride and
epinephrine Adrenaline, also known as epinephrine, is a hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a co ...

epinephrine
(
trade name A trade name, trading name, or business name is a pseudonym A pseudonym () (originally: ψευδώνυμος in Greek) or alias () is a fictitious name that a person or group assumes for a particular purpose, which differs from their original ...
Citanest Forte) *
Lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates ...

Lidocaine
,
bupivacaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

bupivacaine
, and
epinephrine Adrenaline, also known as epinephrine, is a hormone A hormone (from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a co ...

epinephrine
(recommended final concentrations of 0.5, 0.25, and 0.5%, respectively) *
Iontocaine Iontocaine was an anesthetic medication, marketed under the two brand names Numby and Phoresor PM900 by IOMED inc. It is a local anesthetic with vasoconstrictor, administered via iontophoresis through the skin. It can numb up to 10 mm of s ...
, consisting of lidocaine and epinephrine * Septocaine (trade name Septodont), a combination of and epinephrine One combination product of this type is used topically for surface anaesthesia, TAC (5-12%
tetracaine Tetracaine, also known as amethocaine, is an ester local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of ...

tetracaine
,1/2000 (0.05%, 500 , ½ per mille) adrenaline, 4 or 10% cocaine). Using LA with vasoconstrictor is safe in regions supplied by end arteries. The commonly held belief that LA with vasoconstrictor can cause
necrosis Necrosis (from Ancient Greek wikt:νέκρωσις, νέκρωσις ''nékrōsis'' 'death') is a form of cell injury which results in the premature death of Cell (biology), cells in living Tissue (biology), tissue by Autolysis (biology), autol ...
in extremities such as the nose, ears, fingers, and toes (due to constriction of end arteries), is invalidated, since no case of necrosis has been reported since the introduction of commercial lidocaine with epinephrine in 1948.


Ester group

*
Benzocaine Benzocaine, sold under the brand name Orajel amongst others, is an ester An ester is a derived from an (organic or inorganic) in which at least one –OH group is replaced by an –O– () group, as in the substitution reaction of a and ...

Benzocaine
*
Chloroprocaine Chloroprocaine (trade name Nesacaine, Nesacaine-MPF) (often in the hydrochloride salt form as the aforementioned trade names) is a local anesthetic given by Injection (medicine), injection during surgery, surgical procedures and childbirth, labor an ...

Chloroprocaine
*
Cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

Cocaine
* * Dimethocaine (Larocaine) * Piperocaine * Propoxycaine *
Procaine Procaine is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciou ...

Procaine
(Novocaine) * Proparacaine *
Tetracaine Tetracaine, also known as amethocaine, is an ester local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of ...

Tetracaine
(Amethocaine)


Amide group

* Articaine *
Bupivacaine Bupivacaine, marketed under the brand name Marcaine among others, is a medication used to decrease feeling in a specific area. In nerve blocks, it is injected around a nerve that supplies the area, or into the spinal canal's epidural space. It ...

Bupivacaine
*
Cinchocaine Cinchocaine (International Nonproprietary Name, INN/British Approved Name, BAN) or dibucaine (United States Adopted Name, USAN) is an amide local anesthetic. Among the most potent and toxic of the long-acting local anesthetics, current use of cincho ...

Cinchocaine
(Dibucaine) * Etidocaine * Levobupivacaine *
Lidocaine Lidocaine, also known as lignocaine and sold under the brand name Xylocaine among others, is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates ...

Lidocaine
(Lignocaine) * Mepivacaine *
Prilocaine Prilocaine () is a local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consc ...

Prilocaine
*
Ropivacaine Ropivacaine ( rINN) is a local anaesthetic drug belonging to the amino amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula RC(=O)NR′R″, where R, R', and R″ re ...

Ropivacaine
* Trimecaine


Naturally derived

* Saxitoxin * Neosaxitoxin * Tetrodotoxin * Menthol * Eugenol *
Cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

Cocaine
*Spilanthol Most naturally occurring local anesthetics with the exceptions of menthol, eugenol and cocaine are neurotoxins, and have the suffix -toxin in their names. Cocaine binds the intracellular side of the channels while saxitoxin, neosaxitoxin and tetrodotoxin bind to the extracellular side of sodium channels.


History

In Peru, the ancient Inca mythology#Deities, Incas are believed to have used the leaves of the coca, coca plant as a local anaesthetic in addition to its stimulant properties. It was also used for slave payment and is thought to play a role in the subsequent destruction of Inca Empire#Coca, Incas culture when Spaniards realized the effects of chewing the coca leaves and took advantage of it.
Cocaine Cocaine (from , from , ultimately from Quechuan languages, Quechua: ''kúka'') is a tropane alkaloid and stimulant drug obtained primarily from the leaves of two coca species native to South America, ''Erythroxylum coca'' and ''Erythroxylu ...

Cocaine
was first used as a local anesthetic in 1884. The search for a less toxic and less addictive substitute led to the development of the aminoester local anesthetics stovaine in 1903 and procaine in 1904. Since then, several synthetic local anesthetic drugs have been developed and put into clinical use, notably lidocaine in 1943, bupivacaine in 1957, and prilocaine in 1959. The invention of clinical use of local anaesthesia is credited to the Vienna School which included Sigmund Freud (1856-1939), Carl Koller (1857-1944) and Leopold Konigstein (1850-1942). They introduced local anaesthesia, using cocaine, through ‘self-experimation’ on their oral mucosa before introducing it to animal or human experimentation. The Vienna school first started using cocaine as local anaesthesia in ophthalmology and it was later incorporated into ophthalmologic practice. Dr. Halsted and Dr. Hall, in the United States in 1885 described an intraoral anaesthetic technique of blocking the inferior alveolar nerve and the antero-superior dental nerve using 4% cocaine.{ Shortly after the first use of cocaine for topical anesthesia, blocks on peripheral nerves were described. Brachial plexus anesthesia by percutaneous injection through axillary and supraclavicular approaches was developed in the early 20th century. The search for the most effective and least traumatic approach for plexus anesthesia and peripheral nerve blocks continues to this day. In recent decades, continuous regional anesthesia using catheters and automatic pumps has evolved as a method of pain therapy. Intravenous regional anesthesia was first described by August Bier in 1908. This technique is still in use and is remarkably safe when drugs of low systemic toxicity such as prilocaine are used. Spinal anesthesia was first used in 1885, but not introduced into clinical practice until 1899, when August Bier subjected himself to a clinical experiment in which he observed the anesthetic effect, but also the typical side effect of postpunctural headache. Within a few years, spinal anesthesia became widely used for surgical anesthesia and was accepted as a safe and effective technique. Although atraumatic (noncutting-tip) cannulae and modern drugs are used today, the technique has otherwise changed very little over many decades. Epidural anesthesia by a caudal approach had been known in the early 20th century, but a well-defined technique using lumbar injection was not developed until 1921, when Fidel Pagés published his article "Anestesia Metamérica". This technique was popularized in the 1930s and 1940s by Achile Mario Dogliotti. With the advent of thin, flexible catheters, continuous infusion and repeated injections have become possible, making epidural anesthesia still a highly successful technique. Besides its many uses for surgery, epidural anesthesia is particularly popular in obstetrics for the treatment of labor pain.


See also

* Amylocaine * Anesthetic * General anaesthetic, General anesthetic * List of cocaine analogues * List of local anesthetics


References


External links


The American Society of Regional Anesthesia
{{Authority control Anesthesia Local anesthetics,