Vertigo is the impression of motion of oneself or one's surroundings. The management of acute vertigo in the emergency department includes therapy with anticholinergics, antihistamines, benzodiazepines, calcium channel blockers, neuroleptics or glucocorticoids, and maneuvers for benign postural vertigo. Marill and associates compared the efficacy of a benzodiazepine with that of an antihistamine in the treatment of vertigo.

Antihistamines are thought to work as vestibular suppressants, whereas benzodiazepines potentiate the inhibitory γ-aminobutyric acid, centrally inhibiting vestibular responses. Parenteral formulations were used because of better tolerance in patients with nausea and vomiting. Intravenous dimenhydrinate (in a dosage of 50 mg) or lorazepam (in a dosage of 2 mg) were given in a random and blinded manner to 74 consenting patients presenting with acute vertigo. There was no placebo group because some patients in this group would probably not improve without treatment, and withholding treatment would be unethical. At one and two hours after treatment, participants recorded the level of vertigo they experienced in various positions as well as any feeling of nausea or drowsiness. Vertigo during ambulation was noted before treatment and at one and two hours after treatment.

The primary end point, the patient's sensation of vertigo with ambulation, as well as the secondary measurements of efficacy, were found to have improved more after dimenhydrinate treatment. Patients in both groups experienced increased drowsiness at one hour after treatment, but after two hours drowsiness returned to baseline levels in the dimenhydrinate group. Patients in the lorazepam group experienced significantly more drowsiness. Other serious side effects were rare.

The authors conclude that dimenhydrinate treatment of patients with acute vertigo provides a greater decrease in the primary end point, vertigo with ambulation, as well as other secondary end points, than lorazepam. However, the differences in improvement are small. Sedation was greater after lorazepam treatment, which delayed discharge of otherwise symptomatically improved patients. Therefore, dimenhydrinate appears to be the preferred intravenous agent for relief of vertigo in the emergency department setting.