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indicationUsed for treating vertigo, motion sickness, and nausea associated with pregnancy.
pharmacologyDimenhydrinate is an antiemetics drug combination that contains diphenhydramine and theophylline. It is not effective in the treatment of nausea associated with cancer chemotherapy. Dimenhydrinate directly inhibits the stimulation of certain nerves in the brain and inner ear to suppress nausea, vomiting, dizziness, and vertigo. Diphenhydramine and dimenhydinate both reduce vestibular neuronal excitation due to angular or linear acceleration motions.
mechanism of actionThe mechanism by which some antihistamines exert their antiemetic, anti–motion sickness, and antivertigo effects is not precisely known but may be related to their central anticholinergic actions. They diminish vestibular stimulation and depress labyrinthine function. An action on the medullary chemoreceptive trigger zone may also be involved in the antiemetic effect. Dimenhydrinate is a competitive antagonist at the histamine H1 receptor, which is widely distributed in the human brain. Dimenhydrinate's anti-emetic effect is probably due to H1 antagonism in the vestibular system in the brain.
toxicitySymptoms of overdose include delerium, hallucinations, and excitment. Patients may be violent and confused.
biotransformationHepatic (cytochrome P-450 system).
absorptionWell absorbed after oral administration.
half life1 to 4 hours
drug interactionsDonepezil: Possible antagonism of action
Galantamine: Possible antagonism of action
Rivastigmine: Possible antagonism of action
Tacrine: The therapeutic effects of the central acetylcholinesterase inhibitor, Tacrine, and/or the anticholinergic, Dimenhydrinate, may be reduced due to antagonism. The interaction may be beneficial when the anticholinergic action is a side effect. Monitor for decreased efficacy of both agents.
Trimethobenzamide: Trimethobenzamide and Dimenhydrinate, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Monitor for enhanced anticholinergic effects.
Triprolidine: Triprolidine and Dimenhydrinate, two anticholinergics, may cause additive anticholinergic effects and enhance their adverse/toxic effects. Additive CNS depressant effects may also occur. Monitor for enhanced anticholinergic and CNS depressant effects.
Trospium: Trospium and Dimenhydrinate, two anticholinergics, may cause additive anticholinergic effects and enhanced adverse/toxic effects. Monitor for enhanced anticholinergic effects.