THE EFFECT OF DIHYROPYRIDINE CALCIUM-ANTAGONISTS ON HEART-RATE - STUDIES OF FELODIPINE

Blood pressure reduction with dihydropyridine calcium antagonists resu lts in an initial activation of the baroreceptor reflex, which causes a transient increase in heart rate. The present double-blind, crossove r, single-dose study investigated the effect of felodipine extended-re lease (ER) tablets (5 mg), conventional nitrendipine immediate-release tablets (10 mg), and placebo on heart rate in 12 patients with hypert ension. Furthermore, an analysis of pooled heart rate data from four d ouble-blind, monotherapy studies of felodipine ER in hypertension was performed. The effect of felodipine ER 5 to 10 mg once daily (n = 213) compared with placebo (n = 196), on heart rate was measured 24 hours postdose after 4 weeks of treatment. In the single-dose study, the blo od pressure reduction with both felodipine and nitrendipine was associ ated with a modest reflexogenic increase in heart rate. This tended to occur faster with nitrendipine, and the increase in heart rate at 1 h our after administration was significant with nitrendipine, but not wi th felodipine. However, the effect on heart rate was modest for both d rugs. By comparison, the effect of a standardized lunch meat on heart rate (+7 beats/min) was at least as great as that of felodipine (+2 to 6 beats/min). The analysis of pooled heart rate data showed that cont inued treatment with felodipine did not significantly affect heart rat e compared with placebo; the mean difference in change was 1.1 beats/m in (P > 0.20). In conclusion, the recommended starting dose of felodip ine ER for the treatment of hypertension (5 mg once daily) causes an i nitial, clinically insignificant increase in heart rate. During tong-t erm treatment, however, heart rate is completely normalized and no dif ferent from heart rate in patients in the placebo group.