Serum salbutamol concentrations during oral and intravenous treatment in pregnant women.

The serum concentration of salbutamol was determined in 29 pregnant women during oral treatment (4 mg five times per day) and in seven during intravenous infusion (6-30 micrograms/min) because of premature labour. The concentration of salbutamol was determined by combined gas-liquid chromatography mass spectrometry. The mean concentration of serum salbutamol was twice as high during intravenous treatment (24; SD 9 ng/ml), than during oral treatment (12; SD 3 mg/ml). During oral treatment, the salbutamol levels were not correlated to maternal height, weight or the incidence or severity of side-effects. The serum concentrations of salbutamol in patients with twin pregnancies did not differ from those with singleton pregnancies. After stopping intravenous treatment, serum salbutamol levels remained high for several hours and oral treatment can be started 4-6 h after stopping intravenous infusion.