Theophylline clearance during pregnancy.

Theophylline clearance was prospectively studied in eight pregnant asthmatic patients who were receiving maintenance doses of theophylline. The study was designed to analyze theophylline clearance on three occasions during pregnancy and once postpartum. Theophylline clearance during the third trimester was significantly lower than that postpartum. Six patients had clearance measured both during pregnancy and postpartum and of these, five displayed a reduction in theophylline clearance during pregnancy that ranged between 20 and 53%. Two patients required dosage reductions due to symptoms of toxicity. These results indicate that theophylline clearance is frequently reduced during pregnancy, resulting in excessive serum levels. Patients should be observed for toxicity, and theophylline serum levels should be measured more frequently during the last half of pregnancy.