Diuretic-induced hypokalemia and altered renal function.

The effect of a maximal dose of a commonly used diuretic, chlorthalidone, on renal function was assessed in 6 patients with untreated essential hypertension. 100 mg daily of chlorthalidone for a 4-week period produced a significant fall in the plasma potassium concentration and total body potassium content by 16 and 4.2%, respectively. Associated with this change in body potassium status was a 10% decrease in the maximum urine concentrating capacity (p less than 0.01). Renal plasma flow, but not glomerular filtration rate, was also depressed (9.2%) by diuretic therapy. These results suggest that small diuretic induced deficits in the plasma potassium concentration as well as the total body potassium status interfere with renal tubular function.