Cardiovascular effects of infused adenosine in man: potentiation by dipyridamole

Abstract

In a single blind randomized study, eight normal subjects (23-40 years) received on two separate days adenosine as a constant i.v. infusion with doses increasing from 0.005-0.1 mg kg-1 min-1 following either i.v. dipyridamole 0.4 mg kg-1 per 10 min or a corresponding volume of saline. Heart rate, blood pressure and skin temperature were measured. Following saline all subjects tolerated adenosine 0.07 mg kg-1 min-1, six also tolerated 0.09 mg kg-1 min-1. Both heart rate and skin temperature increased with adenosine in a dose-related manner. Thus, adenosine 0.09 mg kg-1 min-1 was associated with an increase in heart rate (mean +/- SD) from baseline before saline with 16 +/- 10 b.p.m. (P less than 0.01) and an increase in skin temperature with 1.3 +/- 0.8 degrees C (P less than 0.02). Dipyridamole, which inhibits the cellular uptake of adenosine was associated with a change in heart rate similar to that induced by adenosine. Furthermore, when adenosine was infused following dipyridamole the changes in heart rate and skin temperature were potentiated as compared with adenosine following saline. Thus, following dipyridamole an increase in heart rate with 15 b.p.m. above baseline was obtained with 0.005 mg kg-1 min-1 of adenosine as compared with 0.08-0.09 mg kg-1 min-1 of adenosine following saline. Blood pressure did not change in any of the studies. Exogenous adenosine in man has a dose-related positive chronotropic effect and a local dilatory effect in the skin microcirculation. Dipyridamole potentiates the cardiovascular effects of infused adenosine in man.