Comparison of the acute and chronic antihypertensive effect of two once-daily doses of spirapril by invasive twenty-four-hour ambulatory blood pressure monitoring.

Spirapril is a new non-sulphydryl angiotensin converting enzyme (ACE) inhibitor which is eliminated mainly through the liver. In a placebo-controlled study the acute and chronic (2 weeks) antihypertensive effects of two doses of spirapril (12.5 and 25 mg) were assessed by invasive 24-h ambulatory blood pressure monitoring in two groups of eight hypertensive subjects. After the first doses of 12.5 and 25 mg, blood pressure rapidly decreased, with a nadir after 4-6 h. At this time, mean arterial pressure was decreased by 24 +/- 2% with the 12.5 and 19 +/- 1% with the 25-mg dose. The antihypertensive response was sustained for almost the whole 24-h period with the 25-mg dose, but it was attenuated during the second half of the 24-h blood pressure monitoring with the 12.5-mg dose, leaving a residual antihypertensive effect of 6 +/- 2% 24 h after dosing. Compared with the response to the first dose, the antihypertensive response after 2 weeks of treatment was similar to that following the 12.5-mg dose, but with the 25-mg dose the response during the second half of the 24-h monitoring period, especially during the night, was attenuated. The reason for this attenuated antihypertensive response during prolonged ACE inhibition remains to be established.