Dose-related effects of intracoronary application of nisoldipine on central and peripheral circulatory parameters

In a randomized study central and peripheral circulatory parameters were determined in 12 anaesthetized mongrel dogs before and after intracoronary injection of nisoldipine and placebo. Administration of 0.2 to 0.8 micrograms/kg nisolpine was followed by a 46% to 62% decrease in coronary vascular resistance and a 109% to 141% increase in myocardial blood flow lasting 10 min. There was no significant change in myocardial contractility or peripheral circulatory parameters. An increase in dosage to 1.6 micrograms/kg did not cause a further increase in myocardial blood flow or decrease in coronary vascular resistance. However, there was a significant decrease in total peripheral resistance of up to 32% and a 36% increase in heart rate attributable to counter-regulation lasting 3 to 5 min. At this dosage level a significant decrease in myocardial contractility and an increase in left ventricular end-diastolic pressure are to be expected. This implies a major dissociation between coronary vascular effects and changes in parameters of myocardial performance and peripheral resistance after intracoronary administration of nisoldipine, an effect which is dose-related. Injection of 0.4 to 0.8 micrograms/kg would seem to be the optimal dosage range for intracoronary administration of nisoldipine producing maximum coronary dilatation without myocardial depression.