The influence of a 7-day medication of either cimetidine (1,000 mg per day) or ranitidine (300 mg per day) on serum ethanol concentrations after a single oral dose of ethanol (0.8 gm per kg body weight) was investigated in a randomized placebo-controlled study in eight male volunteers. Compared with the placebo, cimetidine but not ranitidine produced a significant increase in both the peak serum ethanol concentration (85.9 +/- 3.5 vs. 73.0 +/- 3.2 mg dl-1, p less than 0.02) and in the area under the serum ethanol concentration time curve (350 +/- 19 vs. 304 +/- 25 mg dl-1 hr-1, p less than 0.05). However, the ethanol elimination rate was not affected by cimetidine. When ethanol (1.0 gm per kg body weight) was administered intravenously, cimetidine failed to induce a change in ethanol metabolism. Furthermore, the effect of H2-receptor antagonists was studied in animal experiments. Female Sprague-Dawley rats received a single dose of ethanol (7 or 3 gm per kg body weight) together with an intraperitoneal injection of either cimetidine (120 mg per kg body weight), ranitidine (120 mg per kg body weight) or isotonic saline. After alcohol absorption, ethanol elimination was significantly inhibited by both cimetidine (3.99 +/- 0.39 vs. 5.68 +/- 0.23 mmoles kg-1 hr-1, p less than 0.02) and ranitidine (4.21 +/- 0.14 vs. 5.68 +/- 0.23 mmoles kg-1 hr-1, p less than 0.02) at high ethanol concentrations (60 to 20 mM) but not at blood ethanol concentrations below 20 mM.(ABSTRACT TRUNCATED AT 250 WORDS)

A microsomal ethanol oxidizing system (MEOS) is present in the colonic mucosa of the rat. This MEOS metabolizes ethanol to acetaldehyde at the physiological pH of 7.4. Alcohol dehydrogenase or catalase are not involved in the reaction. The Michaelis Menten constant of the reaction is 13.7 +/- 0.3 mM and the maximal velocity is 219 +/- 30 pmoles acetaldehyde/mg microsomal protein X min. Bacterial ethanol metabolism does not contribute to the acetaldehyde production in the colonic MEOS. Chronic ethanol consumption has no effect on colonic MEOS activity. In addition, chronic ethanol ingestion does not affect colonic microsomal NADPH-cytochrome-c-reductase nor benzo(a) pyrene hydroxylase activity.

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