CHANGES IN THE EFFECTS OF NIZATIDINE AND FAMOTIDINE ON CARDIAC-PERFORMANCE AFTER PRETREATMENT WITH RANITIDINE

This was an open, randomized study of the cardiovascular effects of th e histamine H-2 receptor antagonists ranitidine, famotidine, and nizat idine after single oral doses alone or in combination in healthy volun teers. When compared with placebo ranitidine (450 mg) did not have any haemodynamic effects. Nizatidine (300 mg) caused significant falls in heart rate and cardiac output. Famotidine (40 mg) caused significant falls in stroke volume and cardiac output and an increase in pre-eject ion period. Pretreatment with ranitidine abolished the haemodynamic ef fects of nizatidine and caused a time-shift of 2 h in the onset of the cardiovascular effects of famotidine. The difference in the results f or nizatidine and famotidine can be explained by the longer half-life of famotidine. Vascular effects are assumed to be responsible for impa irment of cardiac performance by famotidine.