dimenhydramin

Dimenhydrinate, commonly marketed under brand names such as Dramamine, is an over-the-counter antiemetic used to prevent and treat motion sickness and related nausea. It is a chemical salt formed from diphenhydramine, an antihistamine, and chlorotheophylline, a stimulant. The combination provides antiemetic effect with reduced daytime sleepiness compared with diphenhydramine alone.

Mechanism of action: Dimenhydrinate acts as a histamine H1 receptor antagonist and has anticholinergic properties. By blocking histaminic inputs to the vomiting center and reducing vestibular stimulation, it can lessen the sensation of nausea and the urge to vomit. The onset of action is typically within 15 to 30 minutes after oral dosing, with a duration of effects around 3 to 6 hours.

Administration and dosage: For adults, the usual dose is 50 mg every four to six hours as needed, not to exceed 300 mg per day. Dosing for children varies by age; caregivers should follow label directions or consult a clinician. Dimenhydrinate is available as tablets, chewable tablets, and liquid formulations; it should be taken with a full glass of water. Avoid driving or operating heavy machinery until you know how it affects you, as drowsiness is common.

Safety and precautions: Common side effects include drowsiness, dizziness, dry mouth, and blurred vision. Less common but serious effects can include confusion, urinary retention, and rapid heart rate in susceptible individuals. Alcohol and other central nervous system depressants can intensify sedation. It should be used with caution in older adults and in individuals with glaucoma, urinary retention, or certain stomach or kidney conditions, and during pregnancy or breastfeeding only after medical advice.