The renin‐angiotensin system during converting enzyme inhibition with captopril in patients with severe treatment‐resistant hypertension

The effect of captopril on blood pressure (BP) and various components of the renin-angiotensin system was assessed in ten severely hypertensive patients. Captopril acutely reduced the BP with a maximum decrease of 23% at 90-120 min. Maintenance treatment with captopril alone could not control the BP in any of the patients. Addition of hydrochlorothiazide markedly reduced the BP, while supplementation with propranolol caused no consistent changes. Three patients attained a supine diastolic blood pressure (SDBP) less than or equal to 90 mmHg. Only two patients had a fall in SDBP less than 10 mmHg. One patient stopped because of taste disturbances. Monitoring the renin-angiotensin system showed suppressed plasma concentrations of angiotensin II and increased levels of angiotensin I and renin, indicating the inhibition of converting enzyme activity. Plasma concentration of renin substrate decreased significantly. This observation has important implications for the methodology of renin assays. Captopril is an effective alternative in the treatment of hypertensive patients not readily controlled with conventional therapy.