Neurohormonal responses to antihypertensive treatment with captopril or hydrochlorothiazide

In order to assess the neurohormonal responses to oral administration of two drugs with different antihypertensive mechanisms, and their implications for long-term efficacy, we studied the changes in plasma renin activity, aldosterone, catecholamines and blood pressure after two cross-over periods of treatment with captopril and hydrochlorothiazide for three months in 14 patients with moderate essential hypertension. Similar levels of plasma renin activity were achieved with both but plasma levels of noradrenaline and aldosterone rose with hydrochlorothiazide (P less than 0.005 and P less than 0.05). Dopamine levels decreased with captopril. Six patients on hydrochlorothiazide had potassium levels under 3.5 mmol/l. Captopril and hydrochlorothiazide were effective in controlling blood pressure in 78% and 50% of the patients respectively, but in cases where noradrenaline was significantly increased after treatment, the effect on diastolic blood pressure was less (P less than 0.05). These data suggest that captopril is highly effective for blood pressure control and that the neurohormonal responses to the drug probably provide additional benefits for long-term therapy in hypertension.