Amoxicillin is an

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy, ...

medication used to treat a number of

bacterial infection Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often beneficial but others can cause infectious diseases. The number of th ...

s. These include

middle ear infection Otitis media is a group of inflammatory diseases of the middle ear. One of the two main types is acute otitis media (AOM), an infection of rapid onset that usually presents with ear pain. In young children this may result in pulling at the ear, ...

strep throat Streptococcal pharyngitis, also known as streptococcal sore throat (strep throat), is pharyngitis (an infection of the pharynx, the back of the throat) caused by ''Streptococcus pyogenes'' a gram-positive, group A streptococcus. Common symptom ...

pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severi ...

skin infections Skin and skin structure infections (SSSIs), also referred to as skin and soft tissue infections (SSTIs), or acute bacterial skin and skin structure infections (ABSSSIs), are infections of skin and associated soft tissues (such as loose connectiv ...

, and

urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidne ...

s among others. It is taken

by mouth Oral administration is a route of administration where a substance is taken through the mouth. Per os abbreviated to P.O. is sometimes used as a direction for medication to be taken orally. Many medications are taken orally because they are i ...

, or less commonly by injection. Common adverse effects include nausea and rash. It may also increase the risk of

yeast infections Candidiasis is a fungal infection due to any type of '' Candida'' (a type of yeast). When it affects the mouth, in some countries it is commonly called thrush. Signs and symptoms include white patches on the tongue or other areas of the mouth ...

and, when used in combination with clavulanic acid,

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin ...

. It should not be used in those who are allergic to

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...

. While usable in those with kidney problems, the dose may need to be decreased. Its use in

pregnancy Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occurs by sexual intercourse, but ...

and

breastfeeding Breastfeeding, or nursing, is the process by which human breast milk is fed to a child. Breast milk may be from the breast, or may be expressed by hand or pumped and fed to the infant. The World Health Organization (WHO) recommends that bre ...

does not appear to be harmful. Amoxicillin is in the beta-lactam family of antibiotics. Amoxicillin was discovered in 1958 and came into medical use in 1972. Amoxil was approved for medical use in the United States in 1974, and in the United Kingdom in 1977. It is on the (WHO)

World Health Organization's List of Essential Medicines The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health s ...

. It is one of the most commonly prescribed antibiotics in children. Amoxicillin is available as a

generic medication A generic drug is a pharmaceutical drug that contains the same chemical substance as a drug that was originally protected by chemical patents. Generic drugs are allowed for sale after the patents on the original drugs expire. Because the active c ...

. In 2020, it was the 40th most commonly prescribed medication in the United States, with more than 15million prescriptions.

Medical uses

Amoxicillin is used in the treatment of a number of infections, including acute otitis media, streptococcal pharyngitis,

s, ''

Salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are ''Salmonella enterica'' and '' Salmonella bongori''. ''S. enterica'' is the type species and is fur ...

'' infections,

Lyme disease Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the '' Borrelia'' bacterium, which is spread by ticks in the genus '' Ixodes''. The most common sign of infection is an expanding red rash, known as erythema ...

, and

chlamydia Chlamydia, or more specifically a chlamydia infection, is a sexually transmitted infection caused by the bacterium '' Chlamydia trachomatis''. Most people who are infected have no symptoms. When symptoms do appear they may occur only several w ...

infections.

Acute otitis media

Children with acute otitis media who are younger than six months of age are generally treated with amoxicillin or other antibiotics. Although most children with acute otitis media who are older than two years old do not benefit from treatment with amoxicillin or other antibiotics, such treatment may be helpful in children younger than two years old with acute otitis media that is bilateral or accompanied by ear drainage. In the past, amoxicillin was dosed three times daily when used to treat acute otitis media, which resulted in missed doses in routine ambulatory practice. There is now evidence that two times daily dosing or once daily dosing has similar effectiveness.

Respiratory infections

Amoxicillin and amoxicillin-clavulanate have been recommended by guidelines as the drug of choice for bacterial

sinusitis Sinusitis, also known as rhinosinusitis, is inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include thick nasal mucus, a plugged nose, and facial pain. Other signs and symptoms may include fever, he ...

and other respiratory infections. Most sinusitis infections are caused by viruses, for which amoxicillin and amoxicillin-clavulanate are ineffective, and the small benefit gained by amoxicillin may be overridden by the adverse effects. Amoxicillin is recommended as the preferred first-line treatment for community-acquired pneumonia in adults by the

National Institute for Health and Care Excellence The National Institute for Health and Care Excellence (NICE) is an executive non-departmental public body of the Department of Health and Social Care in England that publishes guidelines in four areas: * the use of health technologies withi ...

, either alone (mild to moderate severity disease) or in combination with a

macrolide The Macrolides are a class of natural products that consist of a large macrocyclic lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, may be attached. The lactone rings are usually 14-, 15-, or 16-membered. M ...

. The World Health Organization (WHO) recommends amoxicillin as first-line treatment for pneumonia that is not "severe". Amoxicillin is used in post-exposure inhalation of

anthrax Anthrax is an infection caused by the bacterium '' Bacillus anthracis''. It can occur in four forms: skin, lungs, intestinal, and injection. Symptom onset occurs between one day and more than two months after the infection is contracted. The s ...

to prevent disease progression and for prophylaxis.

''H. pylori''

It is effective as one part of a multi-drug regimen for treatment of stomach infections of ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, microaerophilic, spiral (helical) bacterium usually found in the stomach. Its helical shape (from which the genus name, helicobacter, derives) is th ...

''. It is typically combined with a proton-pump inhibitor (such as omeprazole) and a macrolide antibiotic (such as

clarithromycin Clarithromycin, sold under the brand name Biaxin among others, is an antibiotic used to treat various bacterial infections. This includes strep throat, pneumonia, skin infections, '' H. pylori'' infection, and Lyme disease, among others. Clar ...

); other drug combinations are also effective.

Lyme borreliosis

Amoxicillin is effective for treatment of early cutaneous

Lyme borreliosis Lyme or LYME may refer to: * Lyme disease, an infectious disease carried by ticks caused by bacteria of the genus ''Borrelia'' Places United Kingdom * Lyme, an alternative name of Lyme Handley, a civil parish in Cheshire ** Lyme Park, an estate ...

; the effectiveness and safety of oral amoxicillin is neither better nor worse than common alternatively-used antibiotics.

Skin infections

Amoxicillin is occasionally used for the treatment of skin infections, such as

acne vulgaris Acne, also known as ''acne vulgaris'', is a long-term skin condition that occurs when dead skin cells and oil from the skin clog hair follicles. Typical features of the condition include blackheads or whiteheads, pimples, oily skin, and ...

. It is often an effective treatment for cases of acne vulgaris that have responded poorly to other antibiotics, such as doxycycline and minocycline.

Infections in infants in resource-limited settings

Amoxicillin is recommended by the World Health Organization for the treatment of infants with signs and symptoms of pneumonia in resource-limited situations when the parents are unable or unwilling to accept hospitalization of the child. Amoxicillin in combination with

gentamicin Gentamicin is an antibiotic used to treat several types of bacterial infections. This may include bone infections, endocarditis, pelvic inflammatory disease, meningitis, pneumonia, urinary tract infections, and sepsis among others. It is not ...

is recommended for the treatment of infants with signs of other severe infections when hospitalization is not an option.

Prevention of bacterial endocarditis

It is also used to prevent

bacterial endocarditis Infective endocarditis is an infection of the inner surface of the heart, usually the valves. Signs and symptoms may include fever, small areas of bleeding into the skin, heart murmur, feeling tired, and low red blood cell count. Complicati ...

and as a pain-reliever in high-risk people having dental work done, to prevent ''

Streptococcus pneumoniae ''Streptococcus pneumoniae'', or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic (under aerobic conditions) or beta-hemolytic (under anaerobic conditions), aerotolerant anaerobic member of the genus Streptococcus. They a ...

'' and other encapsulated bacterial infections in those without

spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .

s, such as people with

sickle-cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red ...

, and for both the prevention and the treatment of

. The United Kingdom recommends against its use for infectious endocarditis prophylaxis. These recommendations do not appear to have changed the rates of infection for infectious endocarditis.

Combination treatment

Amoxicillin is susceptible to degradation by β-lactamase-producing bacteria, which are resistant to most β-lactam antibiotics, such as

. For this reason, it may be combined with clavulanic acid, a β-lactamase inhibitor. This drug combination is commonly called co-amoxiclav.

Spectrum of activity

It is a moderate-spectrum, bacteriolytic, β-lactam antibiotic in the aminopenicillin family used to treat susceptible

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...

and

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

bacteria. It is usually the drug of choice within the class because it is better-absorbed, following oral administration, than other β-lactam antibiotics. In general, ''

Streptococcus ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occu ...

Bacillus subtilis ''Bacillus subtilis'', known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium, found in soil and the gastrointestinal tract of ruminants, humans and marine sponges. As a member of the genus '' Baci ...

Enterococcus ''Enterococcus'' is a large genus of lactic acid bacteria of the phylum Bacillota. Enterococci are gram-positive cocci that often occur in pairs (diplococci) or short chains, and are difficult to distinguish from streptococci on physical charac ...

Haemophilus ''Haemophilus'' is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the family Pasteurellaceae. While ''Haemophilus'' bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of ...

, Helicobacter,'' and '' Moraxella'' are susceptible to amoxicillin, whereas '' Citrobacter,

Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' species are found everywhere in nature. This is thought to be due to distinct sublineages developin ...

'' and ''

Pseudomonas aeruginosa ''Pseudomonas aeruginosa'' is a common encapsulated, gram-negative, aerobic– facultatively anaerobic, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, ''P. aer ...

'' are resistant to it. Some '' E. coli'' and most clinical strains of ''

Staphylococcus aureus ''Staphylococcus aureus'' is a Gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often posit ...

'' have developed resistance to amoxicillin to varying degrees.

Adverse effects

Adverse effect An adverse effect is an undesired harmful effect resulting from a Pharmaceutical drug, medication or other Surgery#Definitions, intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main ...

s are similar to those for other β-lactam antibiotics, including

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...

, vomiting, rashes, and antibiotic-associated

colitis Colitis is swelling or inflammation of the large intestine ( colon). Colitis may be acute and self-limited or long-term. It broadly fits into the category of digestive diseases. In a medical context, the label ''colitis'' (without qualification ...

. Loose bowel movements (diarrhea) may also occur. Rarer adverse effects include mental changes, lightheadedness, insomnia, confusion, anxiety, sensitivity to lights and sounds, and unclear thinking. Immediate medical care is required upon the first signs of these adverse effects. The onset of an allergic reaction to amoxicillin can be very sudden and intense; emergency medical attention must be sought as quickly as possible. The initial phase of such a reaction often starts with a change in mental state, skin rash with intense itching (often beginning in fingertips and around groin area and rapidly spreading), and sensations of fever, nausea, and vomiting. Any other symptoms that seem even remotely suspicious must be taken very seriously. However, more mild allergy symptoms, such as a rash, can occur at any time during treatment, even up to a week after treatment has ceased. For some people allergic to amoxicillin, the adverse effects can be fatal due to

anaphylaxis Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follo ...

. Use of the amoxicillin/clavulanic acid combination for more than one week has caused a drug-induced immunoallergic-type

hepatitis Hepatitis is inflammation of the liver parenchyma, liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes (jaundice), Anorexia (symptom), poor appetite ...

in some patients. Young children having ingested acute overdoses of amoxicillin manifested

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwor ...

, vomiting, and renal dysfunction. There is poor reporting of adverse effects of amoxicillin from clinical trials. For this reason, the severity and frequency of adverse effects from amoxicillin is probably higher than reported from clinical trials.

Nonallergic rash

Between 3 and 10% of children taking amoxicillin (or

ampicillin Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, and endocarditis. It may also be used to prevent group B stre ...

) show a late-developing (>72 hours after beginning medication and having never taken penicillin-like medication previously) rash, which is sometimes referred to as the "amoxicillin rash". The rash can also occur in adults and may rarely be a component of the DRESS syndrome. The rash is described as

maculopapular A maculopapular rash is a type of rash characterized by a flat, red area on the skin that is covered with small confluent bumps. It may only appear red in lighter-skinned people. The term "maculopapular" is a compound: ''macules'' are small, flat ...

or morbilliform ( measles-like; therefore, in medical literature, it is called "amoxicillin-induced morbilliform rash".). It starts on the trunk and can spread from there. This rash is unlikely to be a true allergic reaction and is not a contraindication for future amoxicillin usage, nor should the current regimen necessarily be stopped. However, this common amoxicillin rash and a dangerous allergic reaction cannot easily be distinguished by inexperienced persons, so a healthcare professional is often required to distinguish between the two. A nonallergic amoxicillin rash may also be an indicator of infectious mononucleosis. Some studies indicate about 80-90% of patients with acute Epstein Barr virus infection treated with amoxicillin or ampicillin develop such a rash. Image:Amoxicillin rash 3 hours after 17th dose.JPG, Nonallergic amoxicillin rash eight days after first dose: This photo was taken 24 hours after the rash began. Image:Amoxicillin rash 11 hours after 17th dose.JPG, Eight hours after the first photo, individual spots have grown and begun to merge. Image:Amoxicillin rash 26 hours after 17th dose.JPG, At 23 hours after the first photo, the color appears to be fading, and much of rash has spread to confluence.

Interactions

Amoxicillin may interact with these drugs: *

Anticoagulants Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where they ...

(

dabigatran Dabigatran, sold under the brand name Pradaxa among others, is an anticoagulant used to treat and prevent blood clots and to prevent stroke in people with atrial fibrillation. Specifically it is used to prevent blood clots following hip or ...

warfarin Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent ...

).British National Formulary 57 March 2009 * Cancer treatment (

methotrexate Methotrexate (MTX), formerly known as amethopterin, is a chemotherapy agent and immune-system suppressant. It is used to treat cancer, autoimmune diseases, and ectopic pregnancies. Types of cancers it is used for include breast cancer, leuke ...

). * Uricosuric drugs. *

Typhoid Typhoid fever, also known as typhoid, is a disease caused by '' Salmonella'' serotype Typhi bacteria. Symptoms vary from mild to severe, and usually begin six to 30 days after exposure. Often there is a gradual onset of a high fever over several ...

vaccine A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. ...

Probenecid Probenecid, also sold under the brand name Probalan, is a medication that increases uric acid excretion in the urine. It is primarily used in treating gout and hyperuricemia. Probenecid was developed as an alternative to caronamide to competitiv ...

reduces renal excretion and increases the blood levels of amoxicillin. * Oral contraceptives may become less effective. *

Allopurinol Allopurinol is a medication used to decrease high blood uric acid levels. It is specifically used to prevent gout, prevent specific types of kidney stones and for the high uric acid levels that can occur with chemotherapy. It is taken by mouth ...

(gout treatment).

Pharmacology

Amoxicillin (α-amino-p-hydroxybenzyl penicillin) is a semisynthetic derivative of penicillin with a structure similar to ampicillin but with better absorption when taken by mouth, thus yielding higher concentrations in blood and in urine. Amoxicillin diffuses easily into tissues and body fluids. It will cross the placenta and is excreted into breastmilk in small quantities. It is metabolized by the liver and excreted into the urine. It has an onset of 30 minutes and a half-life of 3.7 hours in newborns and 1.4 hours in adults. Amoxicillin attaches to the cell wall of susceptible bacteria and results in their death. It also is a bactericidal compound. It is effective against streptococci, pneumococci, enterococci, ''Haemophilus influenzae'', ''Escherichia coli'', ''Proteus mirabilis'', ''Neisseria meningitidis'', ''Neisseria gonorrhoeae'', ''Shigella'', ''Chlamydia trachomatis'', ''Salmonella'', ''Borrelia burgdorferi'', and ''Helicobacter pylori''. As a derivative of

, amoxicillin is a member of the

family and, like penicillins, is a β-lactam antibiotic. It inhibits

cross-link In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...

age between the linear peptidoglycan polymer chains that make up a major component of the bacterial

cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mec ...

. It has two

ionizable Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...

groups in the physiological range (the amino group in alpha-position to the amide carbonyl group and the carboxyl group).

History

Amoxicillin was one of several semisynthetic derivatives of 6-aminopenicillanic acid ( 6-APA) developed by the Beecham Group in the 1960s. It became available in 1972 and was the second aminopenicillin to reach the market (after

in 1961). Co-amoxiclav became available in 1981.

Society and culture

Economics

Amoxicillin is relatively inexpensive. In 2022, a survey of 8 generic antibiotics commonly prescribed in the United States found their average cost to be about $42.67, while amoxicillin was sold for $12.14 on average.

Modes of delivery

Pharmaceutical manufacturers make amoxicillin in tri hydrate form, for oral use available as capsules, regular, chewable and dispersible tablets, syrup and

pediatric Pediatrics ( also spelled ''paediatrics'' or ''pædiatrics'') is the branch of medicine that involves the medical care of infants, children, adolescents, and young adults. In the United Kingdom, paediatrics covers many of their youth until th ...

suspension for oral use, and as the sodium salt for intravenous administration. An extended-release is available. The intravenous form of amoxicillin is not sold in the United States. When an intravenous aminopenicillin is required in the United States, ampicillin is typically used. When there is an adequate response to ampicillin, the course of antibiotic therapy may often be completed with oral amoxicillin. Research with mice indicated successful delivery using

intraperitoneally Intraperitoneal injection or IP injection is the injection of a substance into the peritoneum (body cavity). It is more often applied to animals than to humans. In general, it is preferred when large amounts of blood replacement fluids are needed ...

injected amoxicillin-bearing microparticles.

Names

"Amoxicillin" is the International Nonproprietary Name (INN),

British Approved Name A British Approved Name (BAN) is the official, non-proprietary, or generic name given to a pharmaceutical substance, as defined in the British Pharmacopoeia (BP). The BAN is also the official name used in some countries around the world, because ...

(BAN), and

United States Adopted Name A United States Adopted Name (USAN) is a unique nonproprietary name assigned to a medication marketed in the United States. Each name is assigned by the USAN Council, which is co-sponsored by the American Medical Association (AMA), the United Sta ...

(USAN), while "amoxycillin" is the Australian Approved Name (AAN). Amoxicillin is one of the semisynthetic penicillins discovered by former pharmaceutical company Beecham Group. The patent for amoxicillin has expired, thus amoxicillin and co-amoxiclav preparations are marketed under various brand names across the world.

Veterinary uses

Amoxicillin is also sometimes used as an antibiotic for animals. The use of amoxicillin for animals intended for human consumption (

chicken The chicken (''Gallus gallus domesticus'') is a domestication, domesticated junglefowl species, with attributes of wild species such as the grey junglefowl, grey and the Ceylon junglefowl that are originally from Southeastern Asia. Rooster ...

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Adult females are referred to as cows and adult ...

, and swine for example) has been approved.

References

External links

* {{Portal bar, Medicine Carboxylic acids Enantiopure drugs GSK plc brands Lyme disease Penicillins Phenethylamines Phenols Wikipedia medicine articles ready to translate World Health Organization essential medicines