Dimenhydrinate is an over-the-counter drug used to prevent nausea and motion sickness. It is most commonly used as pills, although it is also available in liquid form and in suppositories. Chemically, dimenhydrinate is a salt of two drugs: Diphenhydramine, and 8-chlorotheophylline, a chlorinated derivative of theophylline.
The effects of dimenhydrinate are very similar to those of diphenhydramine. The main differences are a lower potency, and a longer latency.

Veterinary use:
Dimenhydrinate has successfully been used as an antiemetic and sedative in housepets. It is commonly used to reduce the effects of idiopathic vestibular syndrome.