The effect of low-dose hydrochlorothiazide on blood pressure, serum potassium, and lipoproteins.

Recent clinical trials in hypertension suggest that thiazide diuretics may increase coronary heart deaths in selected patients, possibly through adverse effects on serum potassium, lipids, lipoproteins, and/or apolipoproteins. Administration of smaller doses of diuretics has been recommended to decrease this risk. We evaluated 12.5-mg and 112.5-mg daily doses of hydrochlorothiazide (HCTZ) administered for 1 month to nine postmenopausal black female hypertensives using a double-blind, randomized, crossover design. Both regimens produced significant reductions in sitting diastolic blood pressure, a mean of 11 mm Hg with the high dose and 8 mm Hg with the low dose. The high dose produced a mean 0.7 mEq/L reduction in serum potassium while the low dose caused no change. Both doses produced similar changes in serum lipoproteins. Statistically significant elevations were seen in total cholesterol (approximately 12%), LDL cholesterol (approximately 20%), cholesterol: HDL ratio (approximately 15%), and apolipoprotein B (approximately 20%). Apolipoprotein A1 was significantly reduced (approximately 6%). These results support the use of low doses of HCTZ in mild hypertension to avoid hypokalemia, but suggest that adverse changes in serum lipids will occur.