DOSE-DEPENDENT EFFECT OF BETAHISTINE ON THE VESTIBULOOCULAR REFLEX - A DOUBLE-BLIND, PLACEBO-CONTROLLED STUDY IN PATIENTS WITH PAROXYSMAL VERTIGO

The effect of betahistine on the vestibule-ocular reflex (VOR) was ass essed in 12 patients suffering from paroxysmal vertigo. Only patients who responded to betahistine treatment were admitted to the study in o rder 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 afte r intake, by torsion swing stimulus in the dark, visuo-vestibular inte raction upon simultaneous visual and vestibular stimulation and high f requency 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 torsi on swing experiment and the 32 mg dose in the head shaking experiment. Above these doses, the effect on velocity gain was less marked. Betah istine had no effect on visuo-vestibular interaction or nystagmus dura tion during low frequency torsion. These results suggest that betahist ine has a complex action on H-3 receptors and that the site of action may be in the vestibular nuclei.