[The effect of captopril in nitrate tolerance].

To test whether angiotensin-converting-enzyme (ACE) inhibitor can counteract nitrate tolerance, 15 men (mean age 65 [55-69] years) were studied. They all had an at least 75% stenosis of a main coronary artery branch, proven by coronary angiography no longer than 6 months previously. Each patient underwent six ergometric tests (two each per day on alternate days) at constant exercise level and duration: the sum of S-T segment depressions was measured during the recovery and exercise minutes. The initial ergometry test was done without medication, when the S-T segment sum was 1.15 +/- 0.20 mV. After 25 mg captopril (2nd ergometry period) this sum fell to 0.80 +/- 0.18 mV. Two hours after application of a nitrate plaster the S-T segment sum was 0.55 +/- 0.12 mV (3rd ergometry period). Adding 25 mg captopril a further reduction to 0.35 +/- 0.10 was achieved (4th ergometry period). Subsequently, continuous nitrate application brought about nitrate tolerance. The 5th ergometry period then produced a sum of S-T segment depressions of 0.85 +/- 0.18 mV. Renewed captopril administration reduced this value to 0.50 +/- 0.13 mV (57% of the initial value). The effect of captopril in nitrate tolerance is apparently due to an addition of the anti-ischaemic action of the ACE inhibitor (31%) and the residual effect of the nitrate (26%).