Transfer of terbutaline into breast milk

Terbutaline has been determined in milk and plasma from 4 nursing mothers treated with Bricanyl tablets (2.5 or 5 mg, 3 times daily) because of obstructive lung disease. Both doses produced milk concentrations of terbutaline in the range 2.5-4.6 ng/mL, which were similar to or higher than the concentrations found in plasma. The highest milk:plasma concentration ratios (up to 2.9) were observed at the beginning and end of the dosage interval. The infants in this study were estimated to have ingested about 0.4-0.6 micrograms/kg/day of terbutaline base, which corresponds to 0.2-0.7% of the daily dose per kg taken by the mothers. Terbutaline was not detectable in plasma when samples were taken from one of the infants and no symptoms of beta-adrenoceptor stimulation could be found in any of the babies.