Tolerance and Cardiovascular Effects of Single Dose Felodipine/β-Blocker Combinations in Healthy Subjects

Abstract

The effects of single oral doses of 10 mg felodipine and four beta-blockers (100 mg metoprolol, 5 mg pindolol, 80 mg propranolol, and 10 mg timolol) were evaluated alone and in combination in a 10-way crossover, double-blind, placebo-controlled trial in 10 healthy male volunteers randomized to the medication sequence according to a latin square design. Adverse effects were recorded from spontaneous complaints and investigator observations. Heart rate (HR), PR interval, systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured supine, standing, and after treadmill exercise, before and 2 h after drug administration. The adverse effects experienced with felodipine were as expected for a vasodilator. Seven subjects mentioned complaints voluntarily on the combinations while three experienced side effects receiving felodipine or beta-blocker alone. Felodipine increased resting HR significantly. Timolol produced a greater depression of exercise heart rate than the other beta-blockers, indicating that the dose given was not equivalent to that of the other beta-blockers. Pindolol was ineffective in preventing the increase in supine HR produced by felodipine. Felodipine did not alter PR interval at any level of activity, but rate-corrected supine PR interval was prolonged slightly by felodipine. Metoprolol and timolol significantly prolonged standing PR interval. All beta-blockers prolonged exercise PR interval. Felodipine/beta-blocker combinations did not prolong PR interval more than beta-blockers alone. Prolonged PR interval was the result of reduced HR and direct inhibition of atrioventricular (AV) conduction. Only timolol and the timolol/felodipine combination lowered supine systolic blood pressure significantly. Timolol and all beta-blocker/felodipine combinations reduced exercise SBP significantly.