Comparative effects of verapamil, tiapamil, diltiazem and nifedipine on systemic and splanchnic hemodynamics in man.

The vasodilating effects of verapamil, tiapamil, diltiazem and nifedipine on splanchnic and systemic circulation have been investigated in 18 male normotensive subjects by means of the hepatic venous catheter technique, the thermodilution method and systolic time intervals. After a baseline period, calcium antagonists were administered by a primed-constant infusion. Hemodynamic changes were assessed after an adequate equilibration period. Verapamil did not change splanchnic or systemic hemodynamics. Tiapamil decreased diastolic blood pressure and systemic vascular resistance as well as splanchnic vascular resistance, and increased cardiac output. Diltiazem lowered only systolic blood pressure without effecting splanchnic circulation. The most pronounced vasodilating effect was seen with nifedipine. It significantly reduced systolic and diastolic blood pressure, systemic vascular resistance and also splanchnic vascular resistance. Our present data seem to indicate that nifedipine and tiapamil are more effective vasodilators, especially in the splanchnic vascular bed, as compared to verapamil and diltiazem. We conclude that these two calcium antagonists might be useful in the treatment of intestinal (splanchnic) vasoconstriction.