| Abstract: | Effects of amlodipine (AML), a long-acting calcium antagonist, and losartan (LOS), an angiotensin II receptor antagonist, on 24-hr blood pressure profile were compared in 15 patients with essential hypertension. After 4 weeks of placebo period, the patients were treated with AML or LOS in a random cross-over design for 12–16 weeks each. Either drug was given once daily at 0800 and the doses were titrated so that the office blood pressure was reduced lower than 140/90 mmHg. At the end of each period, 24-hr blood pressure was monitored. Average office blood pressure was lowered from 158 ± 2/ 98 ± 2 mmHg to 134 ± 1/87 ± 1 mmHg by AML and 134 ± 2/88 ± 1 mmHg by LOS. Average 24-hr blood pressure was also reduced from 144 ± 3/ 92 ± 2 mmHg to 131 ± 2/84 ± 2 mmHg by AML and 135 ± 3/85 ± 2 mmHg by LOS. The averaged 24-hr systolic blood pressure was significantly lower in AML than in LOS (p < 0.05). Then, the 24-hr blood pressure was analyzed for four segments; morning (0530–0900 h), daytime (0930–1800 h), evening (1830–2300 h) and night (2330–0500 h). Although the daytime blood pressure was comparable between AML and LOS, systolic blood pressure in the evening and morning hours were lower in AML than in LOS (133 ± 2 vs. 138 ± 3 mmHg, p < 0.01; 129 ± 3 vs. 134 ± 4, p < 0.05). Trough to peak ratio of antihypertensive effect on systolic blood pressure was significantly greater in AML than in LOS (62 ± 5% vs. 55 ± 4%, p < 0.05). Either drug did not cause reflective increase in pulse rate over 24 hours. These results suggest that both AML and LOS are equally effective in lowering daytime blood pressure without eliciting reflex tachycardia, however, the antihypertensive effect of AML lasts longer than that of LOS. Such information seems important to achieve 24-hr blood pressure control using these drugs. |
