The effect of potassium and potassium plus magnesium supplementation on ventricular extrasystoles in mild hypertensives treated with hydrochlorothiazide.

Eleven mild hypertensives with base-line ventricular extrasystoles underwent a 24-week period of treatment with hydrochlorothiazide 50 mg daily. After 8 weeks of treatment either potassium as hydrochloride 1 g twice daily, or a combination of potassium hydrochloride 1 g and magnesium hydroxide 500 mg twice daily was added to the diuretic therapy in a randomised, double-blind, cross-over design. Each treatment period lasted 8 weeks. Supplementation with potassium or potassium plus magnesium resulted in a clear trend for suppression of ventricular ectopic activity. There was no difference in ventricular extrasystoles between the two supplementation groups. Supplementation with potassium plus magnesium but not with potassium only, resulted in a significant rise in serum potassium values (P less than 0.01). Our study suggests that potassium should be supplemented in thiazide-treated hypertensives who are prone to develop ventricular extrasystoles. Addition of magnesium to potassium supplementation does not result in further improvement in ventricular ectopic suppression.