Comparison of the Parenteral histamine2-receptor antagonists

The chemical structure, pharmacokinetic properties, and drug-drug interaction profiles of the parenterally available histamine2 (H2)-receptor antagonists were compared. Famotidine is a guanidinothiazole derivative, ranitidine contains an aminomethylfuran ring, and cimetidine has an imidazole ring. Data from the literature indicate that because of its chemical structure famotidine has a much greater potency and affinity for the H2-receptor and a notable lack of drug-drug interactions when compared with ranitidine and cimetidine. As a result, famotidine should be considered the H2-receptor antagonist of choice for critically ill patients who require gastric-acid suppression and at the same time are being treated with other drugs that depend on the cytochrome P-450 mixed-function oxidase system for their metabolism and/or on renal tubular mechanisms for their excretion.