Prediction of sustained antihypertensive efficacy of chronic captopril therapy: Relationships to immediate blood pressure response and control plasma renin activity

The blood pressure (BP) lowering effect of the orally active angiotensin converting enzyme inhibitor, captopril (SQ 14225), was studied in 59 hypertensive patients maintained on a constant sodium intake. Within 2 hours of the first dose of captopril BP fell from $\text{171}\text{107}$ to a maximum low of $\text{142}\text{92}\text{mm Hg}$ (p < 0.001), and after 4 to 8 days of treatment BP averaged $\text{145}\text{94}\text{mm Hg}$ (p < 0.001). The magnitude of BP drop induced by captopril was significantly correlated to baseline plasma renin activity (PRA) both during the acute phase (r = ?0.38, p < 0.01) and after the 4 to 8-day interval (r = ?0.33, p < 0.01). Because of considerable scatter in individual data, renin profiling was not precisely predictive of the immediate or delayed BP response of separate patients. However, the BP levels achieved following the initial dose of captopril were closely correlated to BP measured after 4 to 8 days of therapy, and appeared to have greater predictive value than control PRA of the long-term efficacy of chronic captopril therapy despite marked BP changes occurring in some patients during the intermediate period. Because of these intermediate BP changes, addition of a diuretic to enhance antihypertensive effectiveness of angiotensin blockade should be restrained for several days after initiation of captopril therapy.