EVALUATION OF THE CENTRAL EFFECTS OF ALCOHOL AND CAFFEINE INTERACTION

1 The dynamic and kinetic interactions of alcohol and caffeine were st udied in a double-blind, placebo controlled, cross-over trial. Treatme nts were administered to eight healthy subjects in four experimental s essions, leaving a 1 week wash-out period between each, as follows: 1) placebo, 2) alcohol (0.8 g kg(-1)), 3) caffeine (400 mg) and 4) alcoh ol (0.8 g kg(-1)) + caffeine (400 mg). 2 Evaluations were performed by means of: 1) objective measures: a) psychomotor performance (critical flicker fusion frequency, simple reaction time and tapping test), b) long latency visual evoked potentials ('pattern reversal'); 2) subject ive self-rated scales (visual analogue scales and profile of mood stat es); 3) caffeine and alcohol plasma concentration determinations. 3 Th e battery of pharmacodynamic tests was conducted at baseline and at +0 .5 h, +1.5 h, +2.5 h, +4 h and +6 h. An analysis of variance was appli ed to the results, accepting a P < 0.05 as significant. The plasma-tim e curves for caffeine and alcohol were analysed by means of model-inde pendent methods. 4 Results obtained with caffeine in the objective mea sures demonstrated a decrease in simple reaction time and an increase in the amplitude of the evoked potentials; the subjects' self-ratings showed a tendency to be more active. Alcohol increased simple reaction time and decreased amplitude of the evoked potentials, although the s ubjects rated themselves as being active. The combination of alcohol caffeine showed no significant difference from placebo in the objecti ve tests; nevertheless, the subjective feeling of drunkenness remained . The area under the curve (AUC) for caffeine was significantly higher when administered with alcohol. 5 Only those objective tests which de monstrated a significant effect with caffeine were able to detect coun teracting effects of caffeine over alcohol.