The inhibition of first-pass metabolism of ethanol by H 2 -receptor antagonists: a tabulated review.

INTRODUCTION: In the 1980s-1990s numerous studies were performed on H2 -receptor antagonist inhibition of ethanol first-pass metabolism. Blood alcohol concentrations warranting possible driving under the influence citations in the United States have subsequently dropped from ≥100 mg/dL to 50 mg/dL (Utah in 2019) (30 mg/dL or zero tolerance in some parts of the world). A reexamination of these studies seemed important.

AREAS COVERED: Papers were compiled that addressed the effect of cimetidine, ranitidine, famotidine, and nizatidine on ethanol metabolism first from a PubMed search and then from citations within these papers. Studies were tabulated for fasting versus fed, ethanol and H2 -receptor antagonist dose and a summary of pharmacokinetic changes.

EXPERT OPINION: At doses of 0.15-0.30 mg/kg in the postprandial state (primarily after breakfast), the H2 -receptor antagonists: cimetidine, ranitidine, famotidine, and nizatidine have all been found to increase the first-pass metabolism of ethanol. With cimetidine, there were sufficient studies to suggest it might be inhibitory outside these restricted states. While the role of inhibition of alcohol dehydrogenase has not been clearly defined, there is circumstantial evidence to support this mechanism. Further studies are required to elucidate the ability of H2 -receptor antagonists to inhibit first-pass metabolism of ethanol.