496 THE EFFECTS OF DIVIDING AMLODIPINE DOSES ON BLOOD PRESSURE CONTROL OVER A 24-HOUR PERIOD AND TROUGH DRUG CONCENTRATION

Abstract

Recently, it is obvious to choice long-acting antihypertensive drugs to treat hypertension. However, even if long-acting antihypertensive drugs was administered, to achieve more ideal blood pressure (BP) control over a 24-hour period, dividing doses seems to have additional benefit. The aim of the study is to investigate whether dividing dose of amlodipine, long-acting calcium channel blocker, was correlated with improvement of BP control over a 24-hour period and increasing trough amlodipine concentration. Ten outpatients with essential hypertension who were taking 5 mg of amlodipine twice a day were included this cross-over study. Four weeks later after taking 5 mg of amlodipine twice a day, blood was collected just before taking amlodipine to evaluate the trough plasma amlodipine concentration, and 8 weeks later ambulatory blood pressure monitoring (ABPM) for the assessment of BP over a 24-hour period and the cardio ankle vascular index (CAVI) for the assessment of arterial stiffness were performed. Then, the dosing regimen was changed to 10 mg once a day and the same tests were performed at the same timings. Mean 24-h BP and morning BP (defined as mean BP from 5:00 a.m. to 7:00 a.m.) during once-a-day amlodipine administration was not higher than that during twice-a-day administration (130.5 ± 11.8/80.1 ± 7.9 mmHg vs. 129.7 ± 7.3/80.1 ± 7.9 mmHg, 126.6 ± 11.2/75.3 ± 7.3 mmHg vs. 124.8 ± 16.7/72.0 ± 18.2 mmHg, respectively). In addition, there were no significant differences in the trough plasma amlodipine concentration and CAVI between once-a-day and twice-a-day administration (20.57 ± 8.22 ng/ml vs. 22.37 ± 7.66 ng/ml, 8.5 ± 1.0 vs. 8.2 ± 1.8, respectively). Dividing doses of amlodipine was not correlated with improvement of 24-hour blood pressure control and trough plasma amlodipine concentration.