Nalbuphine, sold under the brand names Nubain among others, is an

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 us ...

analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...

which is used in the treatment of

pain Pain is a distressing feeling often caused by intense or damaging stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sensory and emotional experience associated with, or resembling that associated with, ...

. It is given by

injection Injection or injected may refer to: Science and technology * Injective function, a mathematical function mapping distinct arguments to distinct values * Injection (medicine), insertion of liquid into the body with a syringe * Injection, in broadca ...

into a

vein Veins are blood vessels in humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated b ...

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

, or

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

Side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...

s of nalbuphine include

sedation Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, ...

, sweatiness, clamminess,

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 Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the Human nose, nose. Vomiting can be the result of ailments like Food-poisoning, foo ...

dizziness Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness. Dizziness is a common medical c ...

vertigo Vertigo is a condition where a person has the sensation of movement or of surrounding objects moving when they are not. Often it feels like a spinning or swaying movement. This may be associated with nausea, vomiting, sweating, or difficulties w ...

dry mouth Xerostomia, also known as dry mouth, is dryness in the mouth, which may be associated with a change in the composition of saliva, or reduced salivary flow, or have no identifiable cause. This symptom is very common and is often seen as a side eff ...

, and

headache Headache is the symptom of pain in the face, head, or neck. It can occur as a migraine, tension-type headache, or cluster headache. There is an increased risk of depression in those with severe headaches. Headaches can occur as a result ...

. Unlike other opioids, it has little to no capacity for

euphoria Euphoria ( ) is the experience (or affect) of pleasure or excitement and intense feelings of well-being and happiness. Certain natural rewards and social activities, such as aerobic exercise, laughter, listening to or making music and da ...

respiratory depression Hypoventilation (also known as respiratory depression) occurs when ventilation is inadequate (''hypo'' meaning "below") to perform needed respiratory gas exchange. By definition it causes an increased concentration of carbon dioxide (hypercapnia ...

. It also has little to no incidence of

dysphoria Dysphoria (; ) is a profound state of unease or dissatisfaction. It is the semantic opposite of euphoria. In a psychiatric context, dysphoria may accompany depression, anxiety, or agitation. In psychiatry Intense states of distress and unea ...

dissociation Dissociation, in the wide sense of the word, is an act of disuniting or separating a complex object into parts. Dissociation may also refer to: * Dissociation (chemistry), general process in which molecules or ionic compounds (complexes, or salts ...

hallucination A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...

s, and related side effects at typical therapeutic doses. Nalbuphine is a mixed agonist/antagonist opioid modulator. Specifically, it acts as a moderate-

efficacy Efficacy is the ability to perform a task to a satisfactory or expected degree. The word comes from the same roots as ''effectiveness'', and it has often been used synonymously, although in pharmacology a pragmatic clinical trial#Efficacy versu ...

partial agonist In pharmacology, partial agonists are drugs that bind to and activate a given receptor, but have only partial efficacy at the receptor relative to a full agonist. They may also be considered ligands which display both agonistic and antagonistic e ...

antagonist An antagonist is a character in a story who is presented as the chief foe of the protagonist. Etymology The English word antagonist comes from the Greek ἀνταγωνιστής – ''antagonistēs'', "opponent, competitor, villain, enemy, riv ...

of the

μ-opioid receptor The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical � ...

(MOR) and as a high-efficacy partial agonist of the

κ-opioid receptor The κ-opioid receptor or kappa opioid receptor, abbreviated KOR or KOP, is a G protein-coupled receptor that in humans is encoded by the ''OPRK1'' gene. The KOR is coupled to the G protein Gi/G0 and is one of four related receptors that bind op ...

(KOR), whereas it has relatively low

affinity Affinity may refer to: Commerce, finance and law * Affinity (law), kinship by marriage * Affinity analysis, a market research and business management technique * Affinity Credit Union, a Saskatchewan-based credit union * Affinity Equity Par ...

for the

δ-opioid receptor The δ-opioid receptor, also known as delta opioid receptor or simply delta receptor, abbreviated DOR or DOP, is an inhibitory 7-transmembrane G-protein coupled receptor coupled to the G protein Gi/G0 and has enkephalins as its endogenous lig ...

(DOR) and

sigma receptor Sigma receptors (σ-receptors) are protein cell surface receptors that bind ligands such as 4-PPBP (4-phenyl-1-(4-phenylbutyl) piperidine), SA 4503 (cutamesine), ditolylguanidine, dimethyltryptamine, and siramesine. There are two subtypes, ...

s. Nalbuphine was patented in 1963US Patent 3393197 - Nusubstituted-14-hydroxydihydronormorphines and was introduced for medical use in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

in 1979. It is marketed in many countries throughout the world.

Medical uses

Nalbuphine is indicated for the relief of moderate to severe pain. It can also be used as a supplement to balanced anesthesia, for preoperative and postoperative analgesia, and for obstetrical analgesia during labor and delivery. However, a 2014 Cochrane Systematic Review concluded that from the included studies, there was limited evidence to demonstrate that "0.1 to 0.3mg/kg nalbuphine compared to placebo might be an effective postoperative analgesic" for pain treatment in children. Further research is therefore needed to compare nalbuphine with other postoperative opioids. Although nalbuphine possesses opioid antagonist activity, there is evidence that in nondependent patients it will not antagonize an opioid analgesic administered just before, concurrently, or just after an injection. Therefore, patients receiving an opioid analgesic, general anesthetics, phenothiazines, or other tranquilizers, sedatives, hypnotics, or other CNS depressants (including alcohol) concomitantly with Nalbuphine may exhibit an additive effect. When such combined therapy is contemplated, the dose of one or both agents should be reduced. In addition to the relief of pain, the drug has been studied as a treatment for morphine induced

pruritus Itch (also known as pruritus) is a sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of sensory experience. Itch has many similarities to pain, and while both are unpleasant ...

(itching). Pruritus is a common side effect of morphine or other pure MOR agonist opioid administration. Kjellberg et al. (2001) published a review of clinical trials relating to the prevalence of morphine induced pruritus and its pharmacologic control. The authors state that nalbuphine is an effective anti-pruritic agent against morphine induced pruritus. The effect may be mediated via central nervous system mechanisms. Pan (1998) summarizes the evidence that activation at the pharmacological level of the KOR antagonizes various MOR-mediated actions in the brain. The author states that the neural mechanism for this potentially very general MOR-antagonizing function by the KOR may have broad applications in the treatment of central nervous system mediated diseases. He does not state, however, that nalbuphine's pharmacological mechanism of action for pruritus is the result of this interaction between the two opioid receptors. Morphine induced pruritus syndrome may also be caused by release of histamine from mast cells in the skin (Gunion et al. (2004). Paus et al. (2006) report that MORs and KORs are located in skin nerves and keratinocytes. Levy et al. (1989) reviewed the literature on the relationship of opioid mediated histamine release from cutaneous mast cells to the etiology of hypotension, flushing and pruritus. The authors investigated the relative abilities of various opioids to induce histamine release mediated increased capillary permeability and tissue edema (“wheal response”) and cutaneous vasodilatation and local redness (“flare response”) when subjects were intradermally injected with 0.02 ml equimolar concentrations of 5 x 10-4 M. Nalbuphine did not produce either a wheal or flare response.

Available forms

Nalbuphine is available in two concentrations, 10 mg and 20 mg of nalbuphine hydrochloride per mL. Both strengths contain 0.94% sodium citrate hydrous, 1.26% citric acid anhydrous, 0.1% sodium metabisulfite, and 0.2% of a 9:1 mixture of methylparaben and propylparaben as preservatives; pH is adjusted, if necessary, with hydrochloric acid. The 10 mg/mL strength contains 0.1% sodium chloride. The drug is also available in a

sulfite Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are wide ...

and paraben-free formulation in two concentrations, 10 mg and 20 mg of nalbuphine hydrochloride per mL. One mL of each strength contains 0.94% sodium citrate hydrous, 1.26% citric acid anhydrous; pH is adjusted, if necessary, with hydrochloric acid. The 10 mg/mL strength contains 0.2% sodium chloride. An investigational extended-release oral formulation is under development b
Trevi Therapeutics

Side effects

Like pure MOR agonists, the mixed agonist/antagonist opioid class of drugs can cause side effects with initial administration of the drug which lessens over time (“ tolerance”). This is particularly true for the side effects of nausea, sedation and cognitive symptoms (Jovey et al. 2003). These side effects can in many instances be ameliorated or avoided at the time of drug initiation by titrating the drug from a tolerable starting dose up to the desired therapeutic dose. An important difference between nalbuphine and the pure MOR agonist opioid analgesic drugs is the “ceiling effect” on respiration (but no ceiling on the analgesic effect). Respiratory depression is a potentially fatal side effect from the use of pure MOR agonists. Nalbuphine has limited ability to depress respiratory function (Gal et al. 1982). As reported in the current Nubain Package Insert (2005), the most frequent side effect in 1066 patients treated with nalbuphine was sedation in 381 (36%). Other, less frequent reactions are: feeling sweaty/clammy 99 (9%), nausea/vomiting 68 (6%), dizziness/vertigo 58 (5%), dry mouth 44 (4%), and headache 27 (3%). Other adverse reactions which may occur (reported incidence of 1% or less) are: :* CNS effects: Nervousness, depression, restlessness, crying, euphoria, flushing, hostility, unusual dreams, confusion, faintness, hallucinations, dysphoria, feeling of heaviness, numbness, tingling, unreality. The incidence of psychotomimetic effects, such as unreality, depersonalization, delusions, dysphoria and hallucinations has been shown to be less than that which occurs with pentazocine. :* Cardiovascular: Hypertension, hypotension,

bradycardia Bradycardia (also sinus bradycardia) is a slow resting heart rate, commonly under 60 beats per minute (BPM) as determined by an electrocardiogram. It is considered to be a normal heart rate during sleep, in young and healthy or elderly adults, a ...

, tachycardia, pulmonary edema. :* Gastrointestinal: Cramps, dyspepsia, bitter taste. :* Respiration: Depression, dyspnea, asthma. :* Dermatological: Itching, burning, urticaria. :* Obstetric: Pseudo-sinusoidal fetal heart rhythm. Other possible, but rare side effects include speech difficulty, urinary urgency, blurred vision, flushing and warmth. A 2014 Cochrane Systematic Review by Schnabel et al., concluded that due to limited data, analysis of adverse events for children treated with nalbuphine compared to other opioids or placebo for postoperative pain, could not be definitively reported.

Overdose

In case of overdose or adverse reaction, the immediate intravenous administration of

naloxone Naloxone, sold under the brand names Narcan (4 mg) and Kloxxado (8 mg) among others, is a medication used to reverse or reduce the effects of opioids. It is commonly used to counter decreased breathing in opioid overdose. Effects begin within ...

(Narcan) is a specific antidote. Oxygen, intravenous fluids, vasopressors and other supportive measures should be used as indicated.

Pharmacology

Pharmacodynamics

Nalbuphine is a

semisynthetic Semisynthesis, or partial chemical synthesis, is a type of chemical synthesis that uses chemical compounds isolated from natural sources (such as microbial cell cultures or plant material) as the starting materials to produce novel compounds with ...

mixed agonist/antagonist opioid modulator of the

phenanthrene Phenanthrene is a polycyclic aromatic hydrocarbon (PAH) with formula C14H10, consisting of three fused benzene rings. It is a colorless, crystal-like solid, but can also appear yellow. Phenanthrene is used to make dyes, plastics and pesticides, e ...

morphinan Morphinan is the prototype chemical structure of a large chemical class of psychoactive drugs, consisting of opiate analgesics, cough suppressants, and dissociative hallucinogens, among others. Structure Morphinan has a phenanthrene core stru ...

series. It is structurally related to the widely used

opioid antagonist An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors. Naloxone and naltrexone are commonly used opioid antagonist drugs which are competitive antagonists that bind to the o ...

and

naltrexone Naltrexone, sold under the brand name Revia among others, is a medication primarily used to manage alcohol or opioid use disorder by reducing cravings and feelings of euphoria associated with substance use disorder. It has also been found t ...

, and to the potent opioid analgesic

oxymorphone Oxymorphone (sold under the brand names Numorphan and Opana among others) is a highly potent opioid analgesic indicated for treatment of severe pain. Pain relief after injection begins after about 5–10 minutes, after oral administration it beg ...

. Nalbuphine binds with high

to the MOR and KOR, and has relatively low affinity for the DOR. It behaves as a moderate-

(or mixed agonist/antagonist) of the MOR and as a high-efficacy partial agonist of the KOR. Nalbuphine has weak or no affinity for the sigma receptor(s) (e.g., K_i > 100,000 nM). Nalbuphine is said to be more

morphine Morphine is a strong opiate that is found naturally in opium, a dark brown resin in poppies (''Papaver somniferum''). It is mainly used as a analgesic, pain medication, and is also commonly used recreational drug, recreationally, or to make ...

-like at lower doses. However at higher doses, it produces more

drunkenness Alcohol intoxication, also known as alcohol poisoning, commonly described as drunkenness or inebriation, is the negative behavior and physical effects caused by a recent consumption of alcohol. In addition to the toxicity of ethanol, the main p ...

, and

. As such, its effects are dose-dependent. Such effects include sedation (21–36%),

(5%),

lightheadedness Lightheadedness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel ...

(1%),

anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

(<1%), dysphoria (<1%),

(<1%),

confusion In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion"

(<1%),

s (<1%),

depersonalization Depersonalization can consist of a detachment within the self, regarding one's mind or body, or being a detached observer of oneself. Subjects feel they have changed and that the world has become vague, dreamlike, less real, lacking in significa ...

(1%), unusual

dream A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, althou ...

s (<1%), and feelings of "unreality" (<1%). Nalbuphine is a potent analgesic. Its analgesic potency is essentially equivalent to that of morphine on a milligram basis, which is based on relative potency studies using intramuscular administration (Beaver et al. 1978). Oral administered nalbuphine is reported to be three times more potent than codeine (Okun et al. 1982). Clinical trials studied single dose experimental oral immediate release nalbuphine tablets for analgesic efficacy over a four- to six-hour time period following administration. Nalbuphine in the 15 to 60 mg range had similar analgesic effects to immediate release codeine in the 30 to 60 mg range (Kantor et al. 1984; Sunshine et al. 1983). Schmidt et al. (1985) reviewed the preclinical pharmacology of nalbuphine and reported comparative data relative to other types of opioid compounds. The authors point out that the nalbuphine moiety is approximately ten times more pharmacologically potent than the mixed opioid agonist/antagonist butorphanol on an "antagonist index" scale which quantitates the drug's ability to act both as an analgesic (via opioid KOR agonism) as well as a MOR antagonist. The opioid antagonist activity of nalbuphine is one-fourth as potent as

nalorphine Nalorphine () (brand names Lethidrone, Nalline), also known as ''N''-allylnormorphine, is a mixed opioid agonist–antagonist with opioid antagonist and analgesic properties. It was introduced in 1954 and was used as an antidote to reverse op ...

and 10 times that of

pentazocine Pentazocine, sold under the brand name Talwin among others, is a painkiller used to treat moderate to severe pain. It is believed to work by activating (agonizing) κ-opioid receptors (KOR) and μ-opioid receptors (MOR). As such it is called an ...

Pharmacokinetics

The

onset of action Onset of action is the duration of time it takes for a drug's effects to come to prominence upon administration. With oral administration, it typically ranges anywhere from 20 minutes to over an hour, depending on the drug in question. Other meth ...

of nalbuphine occurs within 2 to 3 minutes after

intravenous administration Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

, and in less than 15 minutes following subcutaneous or

intramuscular injection Intramuscular injection, often abbreviated IM, is the injection of a substance into a muscle. In medicine, it is one of several methods for parenteral administration of medications. Intramuscular injection may be preferred because muscles have ...

. The

elimination half-life Biological half-life (also known as elimination half-life, pharmacologic half-life) is the time taken for concentration of a biological substance (such as a medication) to decrease from its maximum concentration ( Cmax) to half of Cmax in the bl ...

of nalbuphine is approximately 5 hours on average and in clinical studies the

duration Duration may refer to: * The amount of time elapsed between two events * Duration (music) – an amount of time or a particular time interval, often cited as one of the fundamental aspects of music * Duration (philosophy) – a theory of time and ...

of analgesic activity has been reported to range from 3 to 6 hours.

Chemistry

Nalbuphine is a

derivative In mathematics, the derivative of a function of a real variable measures the sensitivity to change of the function value (output value) with respect to a change in its argument (input value). Derivatives are a fundamental tool of calculus. F ...

and is also known as ''N''-cyclobutylmethyl-14-hydroxydihydronormorphine.

History

Nalbuphine was first synthesized in 1965 and was introduced for medical use in the

in 1979. In the search for opioid analgesics with less abuse potential than pure MOR agonist opioids, a number of semisynthetic opioids were developed. These substances are referred to as mixed

agonist–antagonist In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, beh ...

s analgesics. Nalbuphine belongs to this group of substances. The mixed agonists-antagonists drug class exerts their analgesic actions by agonistic activity at the KOR. While all drugs in this class possess MOR antagonistic activity leading to less abuse potential, nalbuphine is the only approved drug in the mixed agonist–antagonist class listed in terms of its pharmacological actions and selectivities on opioid receptors as a MOR partial agonist or antagonist as well as a KOR agonist (Gustein et al. 2001). Nubain was approved for marketing in the United States in 1978 and remains as the only opioid analgesic of this type (marketed in the U.S.) not controlled under the

Controlled Substances Act The Controlled Substances Act (CSA) is the statute establishing federal government of the United States, federal drug policy of the United States, U.S. drug policy under which the manufacture, importation, possession, use, and distribution of ...

(CSA). When the Controlled Substances Act (CSA) was enacted in 1971, nalbuphine was placed in schedule II. Endo Laboratories, Inc. subsequently petitioned the DEA to exclude nalbuphine from all schedules of the CSA in 1973. After receiving a medical and scientific review and a scheduling recommendation from the Department of Health, Education and Welfare, forerunner to the

Department of Health and Human Services The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the U.S. federal government created to protect the health of all Americans and providing essential human services. Its motto is " ...

, nalbuphine was removed from schedule II of the CSA in 1976. Presently, nalbuphine is not a controlled substance under the CSA. Nalbuphine HCL is currently available only as an injectable in the US and the

European Union The European Union (EU) is a supranational political and economic union of member states that are located primarily in Europe. The union has a total area of and an estimated total population of about 447million. The EU has often been des ...

. Nubain, the Astra USA brand name for injectable nalbuphine HCL, was discontinued from being marketed in 2008 in the United States for commercial reasons (Federal Register 2008); however, other commercial suppliers now provide generic injection formulation nalbuphine for the market.

Society and culture

Brand names

Nalbuphine is marketed primarily under the brand names Nubain, Nalpain, and Nalbuphin. It is also marketed under the brand name Nalufin in

Egypt Egypt ( ar, مصر , ), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia via a land bridge formed by the Sinai Peninsula. It is bordered by the Mediter ...

and Raltrox in

Bangladesh Bangladesh (}, ), officially the People's Republic of Bangladesh, is a country in South Asia. It is the eighth-most populous country in the world, with a population exceeding 165 million people in an area of . Bangladesh is among the mos ...

by Opsonin Pharma Limited, under the brand name Rubuphine in

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

by Rusan Healthcare Pvt Ltd, under the brand name Kinz and Nalbin in

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

by Sami and Global Pharmaceuticals, under the brand name Analin by Medicaids in Pakistan, and under the brand name Exnal by Indus Pharma in Pakistan, among many others.

Legal status

Unlike many other opioids, nalbuphine has a limited potential for

, and in accordance, is rarely abused. This is because whereas MOR agonists produce euphoria, MOR antagonists do not, and KOR agonists like nalbuphine moreover actually produce

. Nalbuphine was initially designated as a Schedule II

controlled substance A controlled substance is generally a drug or chemical whose manufacture, possession and use is regulated by a government, such as illicitly used drugs or prescription medications that are designated by law. Some treaties, notably the Single C ...

in the

along with other opioids upon the introduction of the 1970

. However, its manufacturer, Endo Laboratories, Inc., petitioned the

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...

to remove it from Schedule II in 1973, and after a medical and scientific review, nalbuphine was removed completely from the Controlled Substances Act in 1976 and is not a controlled substance in the United States today. For comparison, MOR full agonists are all Schedule II in the United States, whereas the mixed KOR and MOR agonists/antagonists

butorphanol Butorphanol is a morphinan-type synthetic agonist–antagonist opioid analgesic developed by Bristol-Myers. Butorphanol is most closely structurally related to levorphanol. Butorphanol is available as the tartrate salt in injectable, tablet, and ...

and

are Schedule IV in the United States. In

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, most opioids are classified as Schedule I, but nalbuphine and butorphanol are both listed as Schedule IV substances.

Notes

{{Opioid receptor modulators Analgesics Cyclobutyl compounds 4,5-Epoxymorphinans Ethers Kappa-opioid receptor agonists Mu-opioid receptor agonists Phenols Semisynthetic opioids Tertiary alcohols