Reduction of Salt Intake During Converting Enzyme Inhibitor Treatment Compared With Addition of a Thiazide

Abstract

Abstract A moderate reduction in salt intake lowers blood pressure in individuals with hypertension and improves blood pressure control in those taking a converting enzyme inhibitor. However, it is unclear how effective reduction of salt intake is compared with addition of other drugs, in particular, thiazide diuretics. We directly compared the separate effects on blood pressure of reducing sodium intake or adding a thiazide diuretic in the presence of a converting enzyme inhibitor in a double-blind, randomized, crossover study. We studied 11 subjects with essential hypertension who had been taking 25 mg captopril twice daily for at least 1 month. In the double-blind study, after 1 month of captopril alone, supine blood pressure was 151±5/95±4 (SEM) mm Hg. With the addition of 25 mg hydrochlorothiazide once daily for 1 month, blood pressure fell to 137±5/87±3 mm Hg. When a moderate reduction in salt intake (from 206±26 to 109±20 mmol urinary sodium/24 h) was added to captopril for 1 month, blood pressure was reduced by a similar amount (to 137±4/90±3 mm Hg). Plasma potassium fell during the diuretic treatment (3.9±0.1 to 3.7±0.1 mmol/L, P <.05) but increased nonsignificantly during salt reduction (3.9±0.1 to 4.1±0.2 mmol/L). These results clearly demonstrate that moderate salt reduction, which can be easily achieved, is as effective as a thiazide diuretic in lowering blood pressure in the presence of a converting enzyme inhibitor and has the particular advantage that plasma potassium does not decrease. We recommend that all patients on a converting enzyme inhibitor be advised to reduce their dietary salt intake. This would lead to improved blood pressure control and avoids the need for thiazide treatment in many patients.