Effect of tienilic acid and amiloride in healthy volunteers and in hypertensives with normal renal function.

A double-blind comparison of the effect of tienilic acid (250 mg) and amiloride (5 mg) on renal function in healthy volunteers and of tienilic acid plus amiloride compared to hydrochlorothiazide (50 mg) plus amiloride in patients with mild to moderate essential hypertension for safety and hypotensive efficacy was made. Renal plasma flow ([I] iodohippurate clearance) and glomerular filtration rate ([I] iothalamate clearance and 24 h creatinine clearance) were not affected by tienilic acid or amiloride alone or in combination despite a rise in plasma urea and plasma creatinine (within the normal range) in healthy volunteers. In hypertensive patients tienilic acid and tienilic acid plus amiloride treatments caused a rise in plasma urea and plasma creatinine similar to hydrochlorothiazide and hydrochlorothiazide plus amiloride but no significant change in creatinine clearance occurred with any of the treatments. Tienilic acid and hydrochlorothiazide caused hypokalaemia in the patients which was normalized by addition of amiloride. Fewer subjects became hypokalaemic when amiloride was added to tienilic acid than when tienilic acid was given alone. The antihypertensive effect of tienilic acid and tienilic acid plus amiloride was similar to hydrochlorothiazide and hydrochlorothiazide plus amiloride in patients with hypertension. No effect on blood pressure was observed in the healthy volunteers. Plasma uric acid was significantly reduced by tienilic acid alone and in combination in patients and subjects whereas a significant elevation occurred with hydrochlorothiazide. Side effects were increased when amiloride was added to either tienilic acid or hydrochlorothiazide, but side effects were less common after treatment with tienilic acid than following hydrochlorothiazide. The combination of tienilic acid plus amiloride significantly reduces blood pressure and appears to be well tolerated with no adverse effects on renal function or plasma potassium in patients with mild to moderate hypertension and normal renal function. Addition of amiloride may be useful if hypokalaemia occurs following tienilic acid therapy in such patients.