Acute alcohol tolerance in social drinkers: changes in subjective effects dependent on the alcohol dose and prior...

Using subjective ratings of the degree of alcohol intoxication, the interaction between the drinking history of the subjects, the alcohol dose, and acute alcohol tolerance were examined in light and moderate alcohol consumers (N = 10). Both groups of subjects were tested with doses of alcohol corresponding to 0.5 and 1.0 g/kg. Dose order was random and tests were carried out with an interval of 1 week. Reports of the subjects' previous experience with these doses of alcohol indicated that the moderate consumers ingested the lower (but not the higher) of the doses quite regularly, whereas light consumers were rather inexperienced with both of the doses. Comparison of blood alcohol concentrations as measured by breath and blood analysis yielded slightly different results, the concentrations being significantly higher as measured by breath analysis. This result was mainly associated with the initial phases, where this difference was greatest. Acute tolerance was assessed by comparing the ratings at equal concentrations of alcohol on the ascending and the descending limbs of the alcohol concentration curve. Due to the lag in the measurements of breath and blood alcohol concentrations, the outcome of the evaluations of acute tolerance was also influenced by whether breath or blood alcohol concentrations were used to obtain similar concentrations in both phases. Results based on the breath alcohol concentrations showed that in light alcohol consumers, acute tolerance was demonstrated for both of the doses. In moderate alcohol consumers only the higher of the doses produced evidence for acute tolerance. However, if comparisons are based on blood alcohol concentrations, moderate alcohol consumers also show an apparent acute tolerance for the lower of the doses tested. The present results clearly demonstrate the complexity of the acute tolerance phenomenon, and emphasize the fact that the results are dependent on the dose of alcohol, the subjects' prior experience with alcohol as well as the procedure used for measuring alcohol concentration.