Total body potassium in patients receiving chlorthalidone and metoprolol for hypertension.

Measurements of potassium status were reviewed in 23 hypertensive patients receiving metoprolol either alone or in combination with chlorthalidone or chlorthalidone plus potassium over an average period of nine months. There was no statistically significant change in plasma potassium, total blood cell or total body potassium in patients on long-term metoprolol. Four subjects (17%) in the diuretic groups developed hypokalaemia (serum potassium less than 3.0 mmol/l) in the absence of significant falls in total blood cell or total body potassium. Thus the use of chlorthalidone plus potassium did not provide adequate prophylaxis against hypokalaemia even in metoprolol recipients. The study confirms that monitoring parameters of potassium handling is still necessary in beta-blocker recipients who also receive diuretics alone or in a fixed-dose combination with potassium.