ABSTRACT
The pharmacokinetics of theophylline was determined in six pregnant, nonsmoking women
in labor at term following a single bolus infusion of 5.6 mg/kg of aminophylline over
20 minutes. Cord blood levels were obtained from three babies at delivery. Compared
to values reported in the literature for nonpregnant adult nonsmokers, the volume
distribution (mean 573 ± 53 ml/kg) and clearance rate (mean .88 ± .24 ml/kg/min) of
theophylline is increased in pregnant women, but the half-life (mean 7.95 ± 2 hrs)
remains unaltered. Similar doses of aminophylline can therefore be used in pregnant
and nonpregnant adults who do not smoke cigarettes, but the infusion rate required
to maintain a mean serum concentration of 10 μg/ml (0.5 mg/kg/hr) is almost half that
initially reported in the literature. The serum theophylline concentrations in maternal
venous and mixed cord blood at delivery were almost identical, which implies that
theophylline crosses the placenta rapidly and that the fetus represents a “shallow”
drug compartment.
