Effect of calcium antagonists on basal and digitalis-dependent changes in splanchnic and systemic hemodynamics

We investigated the effects of the calcium antagonists verapamil and tiapamil on basal splanchnic and systemic hemodynamics and digoxin-induced vasoconstriction in 16 healthy men, using the hepatic venous catheter technique, the thermodilution method, and systolic time intervals. After a baseline period, verapamil or tiapamil were given by a primed-constant infusion in six of 16 subjects each, and hemodynamic changes were determined. Thereafter digoxin (1 mg) was concomitantly infused and hemodynamic changes were observed over 105 minutes. Control trials with digoxin alone were performed in seven of 16 subjects. Four of 16 subjects received only placebo. Digoxin provoked an increase in systolic blood pressure and splanchnic vascular resistance. Estimated splanchnic blood flow, mean pulmonary artery pressure, and total electromechanical systole decreased. Verapamil did not change basal hemodynamic parameters. Tiapamil decreased diastolic blood pressure and systemic and splanchnic vascular resistance. Both drugs attenuated the vasoconstricting effect of digoxin on the splanchnic vascular bed. Results indicate that calcium antagonists might be beneficial in treatment of digitalis-induced splanchnic vasospasm.