An experimental study of tolerance among alcohol dependent individuals

Background & objectives: Continued alcohol use leads to tolerance, however, some dependent individuals lose tolerance despite continued alcohol consumption. The exact mechanism for this is not known. This study evaluated tolerance in alcohol dependent patients in a treatment centre using multiple measures. Methods: Male patients with alcohol dependence (DSM III R criteria) were chosen and detoxified in an inpatient setting. On day 14 of detoxification, each subject was given ethanol (0.75 g/kg body wt) mixed in an equal amount of placebo (cola) drink once and an equivalent amount of placebo (cola) during the other occasion in a single blind, randomised, cross over manner. Assessment of each subject was made using multiple measures (clinical, neuro-psychological tests, scales for subjective effect and blood alcohol levels), 30 min after intake of each drink. Results: The subjects (n=26) did not vary under the two conditions (alcohol/placebo) as regards subjective effects, tests on logical memory and Bender Gestalt test (BGT). Cognitive screening scores though different under the two conditions, were within the normative range. Of these 26 subjects, 50 per cent showed clinical signs of intoxication after consumption of alcohol. These two groups (impaired vs unimpaired) were comparable on all base-line clinical parameters, assessment of euphoria and sedation, and various neuropsychological tests except BGT under the two conditions (placebo/alcohol). The non-tolerant (impaired) group scored significantly (P< 0.05) worse on BGT after alcohol consumption. Interpretation & conclusions: The study suggests that clinical tests were more sensitive in detecting intoxication. Further studies are needed to understand the mechanism of loss of tolerance.