Newer H2-receptor antagonists. Clinical pharmacokinetics and drug interaction potential

Since H2-receptor antagonists are widely and successfully used in the treatment of peptic ulcer, several alternatives to the standard agents cimetidine and ranitidine have been developed. Promising 'new' candidates might be famotidine and nizatidine. For proper selection of the appropriate drug, its pharmacokinetic properties and interaction potential should be known. All 'old' and 'new' H2-receptor blockers are eliminated relatively rapidly (t 1/2 ranges from 1.5 to 4 hours), mainly by the renal route (glomerular filtration and tubular secretion). They exhibit a linear disposition and their distribution is similar. Absorption is most complete for nizatidine, whereas famotidine demonstrates the lowest effective plasma concentrations. Since etintidine shares the same imidazole ring structure as cimetidine, it can also impair oxidative drug metabolism in the liver. In this respect, the non-interacting famotidine and nizatidine (like ranitidine) offer a definite advantage. Based on their very similar pharmacokinetic and interaction profiles, these 2 H2-receptor antagonists might be regarded as alternatives to the older drugs in this group, and at least some economic benefits might result from the competition they will provide.