Effect of indapamide on serum and red cell cations, with and without magnesium supplementation, in subjects with mild hypertension.

Unlike some thiazide diuretics, indapamide--a non-thiazide chlorosulphonamide derivative--has been shown to have a magnesium-sparing effect in normotensive subjects. This effect has not been studied in hypertensive subjects. In a randomised double-blind trial indapamide 2,5 mg and placebo were given daily to a group of elderly patients with mild hypertension, with and without supplemental magnesium chloride. Blood pressure and serum and red blood cell cations were measured. The significant antihypertensive effect of indapamide was confirmed. There was no effect of indapamide on serum and red cell magnesium concentrations compared with placebo, both with and without magnesium supplementation. Indapamide induced hypokalaemia with a shift of sodium into the red cells. In this group of elderly hypertensive subjects indapamide induced potassium but not magnesium loss.