Theophylline pharmacokinetics in pregnancy

Area of Science:

• Pharmacology
• Maternal-Fetal Medicine
• Drug Metabolism

Background:

• Theophylline is a medication commonly used for respiratory conditions.
• Pregnancy is known to induce significant physiological changes that can affect drug pharmacokinetics.
• Understanding theophylline pharmacokinetics during pregnancy is crucial for safe and effective treatment.

Purpose of the Study:

• To investigate the serial changes in theophylline pharmacokinetics in pregnant women.
• To assess the impact of pregnancy on theophylline protein binding, distribution, and clearance.
• To determine the clinical implications of these pharmacokinetic alterations.

Main Methods:

• Serial pharmacokinetic studies were conducted in five women during and after pregnancy.
• Measurements included theophylline protein binding, distribution volume, elimination half-life (t1/2), and intrinsic nonrenal and renal clearance.
• Data were compared between different pregnancy trimesters and the postpartum period.

Main Results:

• Theophylline protein binding decreased significantly during the second (11.1%) and third (13.0%) trimesters compared to postpartum (28.1%).
• Distribution volume increased, and elimination t1/2 lengthened in the third trimester.
• Intrinsic nonrenal clearance decreased, but this was counterbalanced by increased intrinsic renal clearance, resulting in no significant reduction in overall unbound clearance.

Conclusions:

• Pregnancy induces substantial alterations in theophylline pharmacokinetics, notably reduced protein binding and increased distribution.
• Despite significant changes in individual clearance pathways, the overall unbound clearance of theophylline does not change significantly during pregnancy or early postpartum.
• These findings suggest that therapeutic drug monitoring may still be necessary to ensure optimal theophylline dosing in pregnant patients.