Alcohol levels are increased in social drinkers receiving ranitidine.

Objective: Ranitidine increases blood alcohol concentrations by decreasing the first pass metabolism of ethanol. The effect of ranitidine on alcohol levels has been found to be variable when using large doses of alcohol or conditions in which its first pass metabolism is known to be minimal. Despite a consensus that the drug increases alcohol levels after small doses of ethanol, this effect has been considered inconsequential, because of the low alcohol levels. However, social drinking comprises repetitive consumption of small doses of alcohol and the ranitidine effect could thereby be potentiated.

Methods: To study this factor, alcohol levels were determined by breath analysis in nine men (social drinkers), after four drinks of 0.15 g/kg ethanol given postprandially every 45 min, before and after ranitidine (150 mg b.i.d. for 7 days).

Results: Their blood alcohol increased with repeated doses, reaching peak values of 24+/-3 mg/dl before ranitidine and 33+/-2 after ranitidine (p = 0.04). In seven of the nine subjects blood alcohol exceeded 25 mg/dl, a level at which impairment of judgment and of finely tuned skills occurs and which exceeds legal limits of driving in some European countries. Moreover, the high levels persisted for a longer time with than without the drug. These effects were associated with a 62% decrease in first pass metabolism.

Conclusion: Under conditions mimicking social drinking, ranitidine increases blood alcohol to levels known to impair psychomotor skills needed for driving.