Metabolic effects of intramuscular and oral administration of ritodrine in pregnancy

The metabolic effects of ritodrine, 80 mg/day, administered intramuscularly in the third trimester of pregnancy to 14 patients for 5 days and per os to 10 patients for 10 days were investigated. Each patient was considered at high risk for premature labor. Intravenous glucose tolerance and insulin, triglyceride, and electrolyte levels were assessed before and at the end of treatment with ritodrine. Intramuscularly or orally administered ritodrine in 10-mg doses 8 times a day did not influence carbohydrate homeostasis. Triglyceride levels fell significantly after intramuscular administration, whereas serum potassium levels increased during treatment. This study suggests that ritodrine administered intramuscularly or orally is metabolically safe in nondiabetic pregnant women.