Renin activity, aldosterone levels and urinary sodium and potassium excretion under tocolytic therapy with salbutamol

The effects of long-term therapy with salbutamol on renin activity, aldosterone levels and urinary sodium and potassium excretion in pregnant women are studied. Salbutamol was given intravenously in a first group of 18 patients in preterm labor, orally in a second group of 9 patients, whereas a third group of 17 patients was taken as control. No significant changes were observed in renin activity and aldosterone levels between the first and the fifth day of intravenous or oral therapy and in 24-h sodium urinary excretion. Only potassium excretion showed a significant decrease (P<0.01) within 24 h from the start of the intravenous therapy, returning to control levels after 48 h. From these results, no replacement of potassium seems to be necessary in patients undergoing tocolytic therapy with betamimetic drugs.