No evidence of CYP3A4 or CYP2C9 induction in humans. Substrate for CYP2D6, CYP1A2, and CYP2C9. No CYP-related drug-drug interactions noted.

Doxylamine is an ethanolamine antihistamine (DrugBank).

Doxylamine is used to treat insomnia and allergy symptoms but is also used in combination with pyridoxine in the treatment of nausea and vomiting in pregnancy (DrugBank). It is taken orally, as a single dose at bedtime, or up to four tablets containing 10 mg doxylamine may be taken in three divided doses when used in combination with pyridoxine for the treatment of nausea and vomiting of pregnancy (DrugDex, SmPC)

Doxylamine is biotransformed in the liver primarily by the cytochrome P450 enzymes CYP2D6, CYP1A2, and CYP2C9, to its principal metabolites N-desmethyl-doxylamine and N,N-didesmethyldoxylamine (SmPC). Doxylamine has showed a marked induction of CYP2B enzymes and a modest induction of CYP3A and CYP2A in mice (Bookstaff 1996) However, there is no evidence that doxylamine is an enzyme inducer of either CYP2C9 or CYP3A4 in humans (IARC 2001). No CYP-related drug interactions are noted in the interactions databases.

No case reports found.