The effects of some drugs on the caloric induced nystagmus.

A striking difference between the two anticholinergic drugs was observed. Atropine only modified the eye speed of the slow phase (mes), whereas scopolamine modified both parameters measured, mes and duration. Amphetamine and caffeine prolonged the duration, leaving the mes unchanged. All antiemetic drugs inhibited both parameters. It is concluded that the effect of a drug on the caloric reaction gives insufficient information in the preclinical evaluation of vestibulo-suppressive drugs.