The Renin‐Angiotensin‐Aldosterone System, Antidiuretic Hormone Levels and Water Balance Under Tocolytic Therapy with Fenoterol and Verapamil

The effects of long-term infusion of fenoterol (a beta 2-sympathomimetic drug) in combination with the calcium antagonist verapamil on water balance, the renin-angiotensin-aldosterone system and antidiuretic hormone during pregnancy were studied. Within two hours of the start of infusion, plasma renin and antidiuretic hormone levels were significantly increased, but plasma aldosterone was strongly decreased. There was a concomitant marked reduction of urinary, sodium, and potassium excretion and a decreased creatinine clearance. The long-lasting reduction of urinary excretion which resulted in an elevated water retention is apparently due to other unknown factors. Results are discussed with special regard to the relationship between water balance disturbances and pulmonary edema.