Ranitidine inhibitory effect

Mathot, R.A. Geus, W.P. Pharmacodynamic modeling of the acid inhibitory effect of ranitidine in patients in an intensive care unit during prolonged dosing characterization of tolerance. Clin. Pharmacol. Ther. 1999, 66 (2), 140-151. 

Interactions of cimetidine and other H -receptor antagonists with the renal secretion of several drugs have been repeatedly described, and comprehensively listed [146]. Thus, cimetidine inhibits renal secretion of procainamide in humans and prolongs its elimination half-life [147,148]. Similar inhibitory effects have been shown on creatinine, ranitidine and many other cationic compounds [149]. 

D. Toxicity Cimetidine is a potent inhibitor of hepatic drug-metabolizing enzymes and may also reduce hepatic blood flow. Cimetidine also has significant antiandrogen effects in patients receiving high doses. Ranitidine has a weaker inhibitory effect on hepatic drug metabolism neither it nor the other H, blockers appear to have endocrine effects. 

Cimetidine is the most potent of the three. Ranitidine has substantially less inhibitory action, and famotidine has negligible effect on the enzyme. 

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