Acetaminophen fails to inhibit ethanol-induced subjective effects in human volunteers

In animals, ethanol causes some of its CNS effects by releasing prostaglandins (PG); this is demonstrated by reports that prostaglandin synthetase inhibitors (PGSIs) diminish ethanol-induced effects. However, use of animals in these studies has precluded testing for subjective effects. We studied the interaction of ethanol and acetaminophen, a PGSI, in a double-blind crossover experiment. Six adult males were given no drug or acetaminophen (0, 325, 650, 1300 or 1950 mg) 75 min before ethanol (total dose=0.625 g/kg; five divided doses). Physiologic, subjective and performance measures were collected. Compared to the no drug condition, ethanol significantly increased ratings of drug "liking," "drunk," "sluggish" and "drug strength" and decreased ratings of "sober." Ethanol increased heart rate and acetaminophen did not diminish or enhance this effect. The failure to antagonize ethanol-induced subjective and physiologic effects by acetaminophen in humans may be due to species differences or inadequate dosage of the PGSI. It is also possible that subjective and certain physiologic effects of ethanol in humans are not mediated by prostaglandin-dependent neural processes. Nevertheless, the finding that at greater than typical analgesic doses, acetaminophen failed to prevent subjective effects of ethanol is of clinical significance.