Hemodynamic studies on cimetidine and ranitidine in anesthetized dogs.

The cardiovascular effects of the H2-receptor-antagonists cimetidine and ranitidine have been compared in a randomized double-blind crossover study. The experiments were performed in seven anesthetized mongrel dogs. Cimetidine (200 mg) and ranitidine (50 mg) were infused i.v. for 2 min. The time interval between cimetidine and ranitidine application was always 3 h. The direct comparison of the drug effects on blood pressure shows a significant difference between cimetidine and ranitidine (P less than 0.001). Apart from the sequence of application, cimetidine causes a significant decrease (P less than 0.01) in total peripheral resistance (-271 +/- 50 dyn . s . cm-5) resulting in a decrease in mean blood pressure (-9 +/- 1.1 mmHg). In contrast to cimetidine, none of the recorded parameters are altered significantly by ranitidine. Heart rate, left ventricular end-diastolic pressure, myocardial contractility (dP/dtmaxLV), mean right atrial pressure, mean pulmonary artery pressure, and cardiac output are not affected significantly by either drug. Due to our results it might be concluded that the cimetidine-induced hypotension is mediated by peripheral vasodilation.