Antihypertensive effect and serum potassium homeostasis: comparison of hydrochlorothiazide and spironolactone alone and in combination.

Hydrochlorothiazide (HCT) and spironolactone (SP), alone and in combination, were utilized in the treatment of 79 adult men with mild to moderate essential hypertension. Comparative effects were determined with regard to anti-hypertensive action, serum potassium homeostasis and BUN. Both HCT and SP, alone and in combination, produced significant anti-hypertensive effects. Anti-hypertensive response to SP was clearly dose-related. All medications produced a moderate and transient elevation of BUN. The most marked differences were observed with regard to serum potassium levels (K). HCT produced a marked decrease in K which persisted through 12 weeks of therapy. SP produced moderate dose-related elevations of K which reverted toward baseline levels between the 4th and 12th weeks of treatment. The "safety advantage" of SP is discussed relative to its role in producing K homeostasis due to its unique mechanism of action.