Source: Υπουργείο Υγείας (CY) Revision Year: 2019 Publisher: MEDOCHEMIE LTD, 1-10 Constantinoupoleos street, 3011 Limassol, Cyprus
Pharmacotherapeutic group: Opium alkaloids and derivatives
ATC code: R05DA09
Dextromethorphan is an antitussive drug. It exerts its antitussive activity by acting on the cough centre in the medulla oblongata, raising the threshold for the cough reflex. A single oral dose of 10-20 mg dextromethorphan produces its antitussive action within 1 hour and lasts for at least 4 hours.
Dextromethorphan is well absorbed from the gut following oral administration. Due to individual differences in the metabolism of dextromethorphan, pharmacokinetic values are highly variable. After the administration of a 20 mg dose of dextromethorphan to healthy volunteers, the Cmax varied from <1 mg/l to 8 mg/l, occurring within 2.5 hours of administration.
Due to extensive pre-systemic metabolism by the liver, detailed analysis of the distribution of orally administered dextromethorphan is not possible.
Dextromethorphan undergoes rapid and extensive first-pass metabolism in the liver after oral administration. Genetically controlled O-demethylation (CYD2D6) is the main determinant of dextromethorphan pharmacokinetics in human volunteers.
It appears that there are distinct phenotypes for this oxidation process resulting in highly variable pharmacokinetics between subjects. Unmetabolised dextromethorphan, together with the three demethylated morphinan metabolites dextrorphan (also known as 3-hydroxy-N-methylmorphinan), 3-hydroxymorphinan and 3-methoxymorphinan have been identified as conjugated products in the urine.
Dextrorphan, which also has antitussive action, is the main metabolite. In some individuals metabolism proceeds more slowly and unchanged dextromethorphan predominates in the blood and urine.
There is insufficient information to determine whether dextromethorphan has mutagenic potential.
There is insufficient information to determine whether dextromethorphan has carcinogenic potential, although such effects have not been associated with these drugs in animal studies.
There is insufficient information to determine whether dextromethorphan has teratogenic potential.
There is insufficient information to determine whether dextromethorphan has potential to impair fertility.
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