RANITIDINE INCREASES THE BIOAVAILABILITY OF IMBIBED ALCOHOL BY ACCELERATING GASTRIC-EMPTYING

To investigate the mechanism of the increase in alcohol bioavailabilit y by ranitidine, we determined by nuclear scan the changes in gastric emptying of a 10% ethanol solution (containing 0.3 g ethanol /kg body weight and 300 mu Ci of technetium-labeled diethylene triamine pentace tic acid) in 8 normal men, before and after treatment with 300 mg rani tidine orally each evening for 1 week. We compared these changes with those of ethanol bioavailability, calculated by integration of the Mic haelis-Menten function over the entire alcohol curves after random i.v . and, on a separate day, oral administration of the same ethanol dose , pre- and post-ranitidine. With ranitidine, we found an acceleration of gastric emptying in 7 of 8 subjects, with 20% shortening of the tim e to 50% emptying (51.8+/-4.1 min vs 64.3+/-3.4, without ranitidine; P <.001 by paired t test). Despite the disappearance (from the stomach) of most of the dose by the end of the blood alcohol curves, only 83+/- 4% reached the systemic blood vs 64+/-4% without ranitidine (P<.02), m ost likely because of a shortened exposure of alcohol dehydrogenase to optimal ethanol concentrations. As a result, after oral but not intra venous alcohol administration, ranitidine increased blood alcohol conc entrations (29+/-4 mg/dl vs 22+/-3, without ranitidine; P<.02), with a corresponding decrease in first pass metabolism of ethanol from 107+/ -16 mg/kg to 47+/-16 (P<.01).