Dose-Dependent Effect of Betahistine on the Vestibulo-Ocular Reflex: A Double-Blind, Placebo Controlled Study in Patients with Paroxysmal Vertigo

Abstract

The effect of betahistine on the vestibulo-ocular reflex (VOR) was assessed in 12 patients suffering from paroxysmal vertigo. Only patients who responded to betahistine treatment were admitted to the study in order to increase the probability of quantifying the effect of the drug on vestibular function. Patients received placebo or 16, 32 or 64 mg betahistine orally under double-blind conditions. Vestibular function was tested a few minutes before intake, and 1,2, 3, 4, 6 and 8 h after intake, by torsion swing stimulus in the dark, visuo-vestibular interaction upon simultaneous visual and vestibular stimulation and high frequency passive head shaking. Betahistine significantly affected the velocity gain of low and high frequency VOR. The reduction in gain was maximal about 4 h after administration of the 16 mg dose in the torsion swing experiment and the 32 mg dose in the head shaking experiment. Above these doses, the effect on velocity gain was less marked. Betahistine had no effect on visuo-vestibular interaction or nystagmus duration during low frequency torsion. These results suggest that betahistine has a complex action on H₃ receptors and that the site of action may be in the vestibular nuclei.

Key Words:

• torsion swing
• visuo-vestibulo-interaction
• vestibular nuclei