Can an angiotensin-converting enzyme inhibitor with a short half-life effectively lower blood pressure for 24 hours?

Twenty-four-hour noninvasive ambulatory blood pressure monitoring was used to study the antihypertensive effect of morning (8 AM) versus evening (10 PM) administration of the new angiotensin-converting enzyme inhibitor quinapril, 20 mg. Eighteen patients with mild to moderate hypertension were studied in a double-blind, crossover fashion after 2 weeks of placebo for 4 weeks of each of the two active treatments. The results show that 20 mg of quinapril given once daily is effective in lowering blood pressure levels throughout a 24-hour period. The 24-hour blood pressure profiles showed a more sustained antihypertensive effect with an evening dose of quinapril compared with a morning dose of quinapril; with the morning dose a smaller reduction in blood pressure was observed during nighttime hours. Evening administration seems preferable, because it produces a more sustained and stable 24-hour blood pressure control probably through a more favorable modulation of tissue angiotensin-converting enzyme inhibition or effect on the adrenergic-induced rise in blood pressure that occurs during early morning hours.