Effects of xylene and alcohol on vestibular and visual functions in man

Ten healthy male volunteers were exposed for 4 h to two concentrations [6 and 11.5 mumol/l (636 and 1,218 mg/m3)] of m-xylene or/and given single doses (0.4 and 0.8 g/kg) of ethyl alcohol. Exposure to two xylene concentrations combined with the higher dose (0.8 g/kg) of alcohol was also conducted. Vestibular functions (positional nystagmus with electronystagmography, body balance) and visual function (flicker fusion) were measured. Both alcohol doses increased body sway and the intensity of nystagmus more than either concentration of xylene did, but they had little effect on visual functions. The effects of alcohol on vestibular functions were dose-dependent. The effects of xylene alone on the vestibular system were rather small, and those on the visual functions negligible. The combined effect of alcohol and the lower concentration of xylene (6 mumol/l) on body sway was additive, but the higher xylene concentration (11.5 mumol/l) antagonized the effect of alcohol on body sway and positional nystagmus. Two subjects experienced nausea and vomited exposure to alcohol and the higher xylene concentration. Mild impairment in visual functions was noted in the combined exposure. Alcohol significantly increased the blood m-xylene concentrations, a finding that suggests that their antagonism was pharmacodynamic rather than pharmacokinetic.