Plasma electrolytes in elderly patients taking fixed combination diuretics.

Plasma potassium and sodium concentrations were measured in a group of elderly patients taking maintenance thiazide diuretic therapy alone, with a potassium supplement or in combination with a potassium sparing diuretic. Fixed dose combinations of a thiazide and potassium sparing diuretic did not significantly reduce the prevalence of hypokalaemia and the combination of amiloride-hydrochlorothiazide was associated with a disproportionate number of cases of hyponatraemia. The desirability of the current widespread use of fixed dose combination diuretics over less expensive single agents is questioned.