A double-blind comparison of the effects of hydrochlorothiazide and tienylic acid (a diuretic with uricosuric properties) in hypertension.

1. A double-blind comparison of the effect of tienylic acid and hydrochlorothiazide on blood pressure was made in patients with moderate hypertension. 2. The antihypertensive effect of 500 mg tienylic acid was comparable to 100 mg hydrochlorothiazide; mean decrease in supine blood pressure after 6 weeks treatment was 20/12 mmHg with tienylic acid and 17/9 mmHg with hydrochlorothiazide. Onset of antihypertensive action was within 1 week and was associated with significant weight loss. 3. Tienylic acid caused a marked decrease in serum uric acid to a mean of 0.18 mmol/1 (n = 11, P less than 0.001), this persisted through the treatment period and returned to placebo values 1 week after treatment ceased. Some patients had uric acid crystaluria and some had post-treatment uric acid levels higher than on placebo. 4. Tineylic acid and hydrochlorothiazide caused mild hypokalemia and alkalosis with proportional decrease in plasma chloride. 5. Blood urea and serum creatinine rose with both drugs and there was an unimportant decline in plasma sodium. 6. Tienylic acid is an effective antihypertensive agent with powerful uricosuric action and appears relatively free of side effects. Further studies are necessary to determine optimal dosage regimes and long term safety.