Dextrorphan (DXO) is a

psychoactive drug A psychoactive drug, psychopharmaceutical, psychoactive agent or psychotropic drug is a chemical substance, that changes functions of the nervous system, and results in alterations in perception, mood, consciousness, cognition or behavior. T ...

of the

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 cor ...

class which acts as an

antitussive Cold medicines are a group of medications taken individually or in combination as a treatment for the symptoms of the common cold and similar conditions of the upper respiratory tract. The term encompasses a broad array of drugs, includin ...

cough suppressant Cold medicines are a group of medications taken individually or in combination as a treatment for the symptoms of the common cold and similar conditions of the upper respiratory tract. The term encompasses a broad array of drugs, includin ...

and

dissociative Dissociatives, colloquially dissos, are a subclass of hallucinogens which distort perception of sight and sound and produce feelings of detachment – dissociation – from the environment and/or self. Although many kinds of drugs are capable of ...

hallucinogen Hallucinogens are a large, diverse class of psychoactive drugs that can produce altered states of consciousness characterized by major alterations in thought, mood, and perception as well as other changes. Most hallucinogens can be categorized ...

. It is the dextrorotatory

enantiomer In chemistry, an enantiomer ( /ɪˈnænti.əmər, ɛ-, -oʊ-/ ''ih-NAN-tee-ə-mər''; from Ancient Greek ἐνάντιος ''(enántios)'' 'opposite', and μέρος ''(méros)'' 'part') – also called optical isomer, antipode, or optical ant ...

of racemorphan; the levorotatory enantiomer is

levorphanol Levorphanol (brand name Levo-Dromoran) is an opioid medication used to treat moderate to severe pain. It is the levorotatory enantiomer of the compound racemorphan. Its dextrorotatory counterpart is dextrorphan. It was first described in Ge ...

. Dextrorphan is produced by O-demethylation of

dextromethorphan Dextromethorphan (DXM) is a medication most often used as a cough suppressant in over-the-counter cold and cough medicines. It is sold in syrup, tablet, spray, and lozenge forms. In 2022, the FDA approved a formulation of it combined with bu ...

CYP2D6 Cytochrome P450 2D6 (CYP2D6) is an enzyme that in humans is encoded by the ''CYP2D6'' gene. ''CYP2D6'' is primarily expressed in the liver. It is also highly expressed in areas of the central nervous system, including the substantia nigra. CYP2 ...

. Dextrorphan is an

NMDA antagonist NMDA receptor antagonists are a class of drugs that work to antagonize, or inhibit the action of, the ''N''-Methyl-D-aspartate receptor ( NMDAR). They are commonly used as anesthetics for animals and humans; the state of anesthesia they induc ...

and contributes to the psychoactive effects of dextromethorphan.

Pharmacology

Pharmacodynamics

The pharmacology of dextrorphan is similar to that of

(DXM). However, dextrorphan is much more potent as an NMDA receptor antagonist as well much less active as a

serotonin reuptake inhibitor A serotonin reuptake inhibitor (SRI) is a type of drug which acts as a reuptake inhibitor of the neurotransmitter serotonin (5-hydroxytryptamine, or 5-HT) by blocking the action of the serotonin transporter (SERT). This in turn leads to increa ...

, but retains DXM's activity as a

norepinephrine reuptake inhibitor A norepinephrine reuptake inhibitor (NRI, NERI) or noradrenaline reuptake inhibitor or adrenergic reuptake inhibitor (ARI), is a type of drug that acts as a reuptake inhibitor for the neurotransmitters norepinephrine (noradrenaline) and epine ...

. It also has more affinity for the opiod receptors than dextromethorphan, significantly so at high doses.

Pharmacokinetics

Dextrorphan has a notably longer

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 ...

than its parent compound, and therefore has a tendency to accumulate in the blood after repeated administration of normally dosed dextromethorphan formulations. It is further converted to 3-HM by

CYP3A4 Cytochrome P450 3A4 (abbreviated CYP3A4) () is an important enzyme in the body, mainly found in the liver and in the intestine. It oxidizes small foreign organic molecules ( xenobiotics), such as toxins or drugs, so that they can be removed from t ...

or glucuronidated.

Society and culture

Legal status

Dextrorphan was formerly a

Schedule I Schedule 1 may refer to: * Schedule I Controlled Substances within the US Controlled Substances Act * Schedule I Controlled Drugs and Substances within the Canadian Controlled Drugs and Substances Act * Schedule I Psychotropic Substances within th ...

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 Sing ...

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 U.S. state, states, a Washington, D.C., federal district, five ma ...

, but was unscheduled on October 1, 1976.

Research

Dextrorphan was under development for the treatment of stroke, and reached

phase II Phase II, Phase 2 or Phase Two may refer to: Media * Marvel Cinematic Universe: Phase Two, six American superhero films from 2013–2015 * ''Star Trek: Phase II'', an unrealized television series based on the characters of Gene Roddenberry's ''S ...

clinical trial Clinical trials are prospective biomedical or behavioral research studies on human subject research, human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel v ...

s for this indication, but development was discontinued.

Environmental presence

In 2021, dextrorphan was identified in >75% of sludge samples taken from 12

wastewater treatment Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environme ...

plants in

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

. The same study associated dextrorphan with

estrogenic Estrogen or oestrogen is a category of sex hormone responsible for the development and regulation of the female reproductive system and secondary sex characteristics. There are three major endogenous estrogens that have estrogenic hormonal acti ...

activity by using

predictive modelling Predictive modelling uses statistics to predict outcomes. Most often the event one wants to predict is in the future, but predictive modelling can be applied to any type of unknown event, regardless of when it occurred. For example, predictive mod ...

, before observing it in

in vitro ''In vitro'' (meaning in glass, or ''in the glass'') studies are performed with microorganisms, cells, or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in biology and ...

References

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Pharmacodynamics Pharmacodynamics (PD) is the study of the biochemical and physiologic effects of drugs (especially pharmaceutical drugs). The effects can include those manifested within animals (including humans), microorganisms, or combinations of organisms ( ...

, titlestyle = background:#ccccff , list1 = {{Ionotropic glutamate receptor modulators {{Monoamine reuptake inhibitors {{Nicotinic acetylcholine receptor modulators {{Opioid receptor modulators {{Sigma receptor modulators Antitussives Dissociative drugs Enantiopure drugs Euphoriants Morphinans Mu-opioid receptor agonists Nicotinic antagonists NMDA receptor antagonists Phenols Serotonin–norepinephrine reuptake inhibitors Sigma agonists