DRUG-INTERACTIONS OF H-2-RECEPTOR ANTAGONISTS

Three drug interactions of nizatidine and of other antisecretory agent s were studied comparatively. First, the effects of nizatidine, cimeti dine and ranitidine on the dispositional kinetics of theophylline were evaluated in chronic obstructive pulmonary disease (COPD) patients. S econd, the effect of magnesium/aluminium hydroxide on the relative bio availability of nizatidine, famotidine, cimetidine and ranitidine was evaluated in healthy volunteers. Finally, the effects of nizatidine an d omeprazole on the dispositional kinetics of phenytoin were evaluated in healthy volunteers. Only cimetidine altered the steady-state kinet ics of oral theophylline, slowing theophylline clearance by 25%. Each of the H-2-receptor antagonists exhibited a modest decline in relative bioavailability when ingested with antacid. Antacid ingestion decreas ed the bioavailability of famotidine, ranitidine and cimetidine by 20- 25%, and the bioavailability of nizatidine by 12%. Each of these effec ts was statistically significant. Finally, it was found that neither o meprazole nor nizatidine affected the single dose kinetics of phenytoi n.