Dimenhydrinate

Dimenhydrinate (marketed as Dramamine, Gravol and many other brand names) is an over-the-counter antiemetic used for the treatment of the symptoms of motion sickness. It is most commonly prepared as tablets, although it is also available in liquid form and in suppositories. Dimenhydrinate is a combination of two drugs: diphenhydramine and 8-chlorotheophylline.

Medical uses

Dimenhydrinate is primarily used to treat nausea, vomiting, and dizziness caused by motion sickness. Dimenhydrinate has also been found to aid in the treatment of ear congestion.

Diphenhydramine is the primary constituent of dimenhydrinate and dictates the primary effect. The main difference relative to pure diphenhydramine is a lower potency due to being combined with 8-chlorotheophylline. By weight, dimenhydrinate is between 53% to 55.5% diphenhydramine.

8-Chlorotheophylline, a chlorinated derivative of theophylline, was added in order to counteract drowsiness. Theophylline is very closely related to caffeine and theobromine, mild central nervous system stimulants. It was thought by scientists that by combining the antiemetic effects of diphenhydramine with a stimulant, the extreme drowsiness induced by the former could be mitigated somewhat by the latter. The sedation caused by diphenhydramine, however, is substantially stronger than the stimulation caused by 8-chlorotheophylline, so the overall effect is still mostly sedating.