HEMODYNAMIC AND RENAL EFFECTS OF FELODIPINE IN YOUNG AND ELDERLY SUBJECTS

Objective: To study the influence of age on renal and haemodynamic eff ects of the calcium antagonist felodipine. Methods: Eight young (mean age 27 years) and eight elderly (mean age 75 years) healthy normotensi ve subjects were given felodipine intravenously for 120 min aiming at close to therapeutic plasma level concentration. Renal blood flow (RBF ) and renal vascular resistance (RVR) was estimated from para-aminohip puric acid (PAH) clearance (51Cr)EDTA clearance was used to measure gl omerular filtration rate (GFR) and used in the calculations of fractio nal excretion (FE) of electrolytes. Impedance cardiography was perform ed to assess stroke volume and for the calculation of cardiac output a nd ejection fraction. Results: At the end of felodipine infusion, the concentration of felodipine was on average 10.0 nmol . l(-1) in young and 12.0 nmol . l(-1) in elderly subjects (NS). During felodipine infu sion blood pressure (BP) decreased from 138/76 to 120/68 in elderly su bjects. The BP in young subjects was 126/74 at basal and 125/70 after infusion of felodipine. The systemic and renal vascular resistance dec reased to a similar extent in young and elderly subjects after felodip ine infusion. Felodipine caused a decrease in systemic vascular resist ance from 25.6 to 23.3 in elderly and from 23.8 to 21.8 in the young s ubjects. Mean values for RVR at baseline and during infusion of felodi pine were significantly higher in the elderly (10.1-15.1) than in the young subjects (5.4-6.7). Felodipine reduced RVR by 10% in the young a nd by 12% in the elderly at the end of infusion. The young subjects ha d 31% higher GFR than the elderly subjects at the start of infusion. F elodipine infusion did not affect GFR. There were no effects on stroke volume and ejection fraction. An initial natriuretic effect was found after infusion of felodipine in the young subjects. The fractional ex cretion of all electrolytes tended to increase after both felodipine a nd placebo, more in the elderly than in the young subjects. Conclusion : The effects of felodipine on central and renal haemodynamics previou sly observed in young and middle-aged subjects also seem to exist in t he elderly. Volume expansion seems to increase the excretion of electr olytes more in elderly than in young people, and therefore the effect of felodipine on natriuresis is more evident in young subjects.