By Marcello Cherchi, MD PhD
For patients
Dimenhydrinate is a medication for motion sickness, and can be helpful for nausea. It can make you feel sleepy, and can make your mouth feel dry. You can get this medication without a prescription in the United States.
For clinicians
Overview
Dimenhydrinate is an oral medication used in the treatment of constitutional motion sensitivity (motion sickness), nausea and disequilibrium. Common adverse effects include drowsiness, dry mouth and cognitive impairment. It is available over-the-counter in the United States.
Introduction
Dimenhydrinate is an oral medication used in the treatment of constitutional motion sensitivity (motion sickness), nausea and disequilibrium.
Pharmacology
Dimenhydrinate is a combination of diphenhydramine (an ethanolamine derivative) and 8‑chlorotheophylline (a chlorinated theophylline derivative) (Zabirowicz and Gan 2019). Dimenhydrinate must be metabolized by the liver for the active ingredient (diphenhydramine) to take effect, so it has a slower action of onset than pure diphenhydramine. The half-life of dimenhydrinate is 3 – 9 hours.
Relevance in otoneurology
The main application of dimenhydrinate in otoneurology is in the management of constitutional motion sensitivity (motion sickness), nausea and disequilibrium. In the management of constitutional motion sensitivity, it has been reported that dimenhydrinate 50 mg is equivalent to a transdermal scopolamine patch, and dimenhydrinate 100 mg is superior to a transdermal scopolamine patch (Nachum et al. 2006).
Adverse effects
The main adverse effects of dimenhydrinate are related to its anti-histaminic activity (drowsiness, dry mouth) and anti-cholinergic activity (cognitive impairment).
Cautions and contraindications
Due to the potential soporific effect of dimenhydrinate, it is preferable to avoid taking this medication before driving or operating machinery.
Other notes
Dimenhydrinate is available over-the-counter in the United States. It is marketed under several brand names, probably the most common of which is Dramamine®.
References
Nachum Z, Shupak A, Gordon CR (2006) Transdermal Scopolamine for Prevention of Motion Sickness. Clinical Pharmacokinetics 45: 543-566. doi: 10.2165/00003088-200645060-00001
Zabirowicz ES, Gan TJ (2019) Pharmacology of postoperative nausea and vomiting. Pharmacology and Physiology for Anesthesia, 2nd edn. Elsevier, Philadelphia, pp 671-692
