Effect of acute and chronic oral administration of alfuzosin on baroreflex function and tremor in man.

1. The effects of the acute and chronic administration of the alpha 1-adrenoceptor antagonist alfuzosin (5 mg twice daily for 7 days) on baroreflex function, physiological tremor and sedation (visual analogue scale) were investigated in six healthy volunteers. 2. Phenylephrine-systolic pressure dose-response curves were shifted (P less than 0.05) to the right by alfuzosin compared with placebo on day 1, and on day 8 prior to the administration of alfuzosin indicating significant alpha-adrenoceptor blockade over 24 h with 5 mg twice daily administration. 3. Baroreflex sensitivity (delta R-R ms mmHg-1 systolic arterial pressure) was reduced (P less than 0.05) by alfuzosin compared with placebo on day 1 (13.8 +/- 2.6 vs 20.6 +/- 3.6 ms mmHg-1) and on day 8 (13.4 +/- 1.7 vs 21.1 +/- 2.7 ms mmHg-1). 4. Maximum power (microV2) or frequency (Hz) of physiological tremor did not change 2 h after alfuzosin administration on day 1 (13.7 +/- 4.4 microV2, 9.2 +/- 0.3 Hz) or day 8 (11.5 +/- 4.3 microV2, 10.0 +/- 0.4 Hz) compared with placebo on day 1 (16.9 +/- 7.5 microV2, 10.0 +/- 0.4 Hz) and day 8 (17.3 +/- 5.7 microV2, 10.2 +/- 0.8 Hz). 5. Alfuzosin 5 mg twice daily did not cause sedation on day 1 or day 8. 6. In conclusion the reduction in baroreflex sensitivity with the alpha-adrenoceptor antagonist alfuzosin may contribute to its antihypertensive activity in reducing the reflex tachycardia associated with its hypotensive action.