Theophylline metabolism after cardiac surgery

Area of Science:

• Pharmacology
• Cardiovascular Surgery
• Drug Metabolism

Background:

• Theophylline pharmacokinetics and metabolism post-cardiac surgery are not well-documented.
• Understanding these effects is crucial for optimizing patient care and medication management.

Purpose of the Study:

• To evaluate the effects of intravenous aminophylline on hemodynamics and theophylline metabolism in adult patients undergoing cardiac surgery.
• To compare theophylline pharmacokinetics between the acute postoperative phase and the recovery phase.

Main Methods:

• Two series of intravenous aminophylline (3 mg/kg/h for 2 hours) were administered to 10 adult patients.
• Blood and urine samples were collected over 24 hours post-administration during the acute (operative day) and recovery (4th/5th postoperative day) phases.
• Hemodynamic parameters (heart rate, cardiac index, blood pressure) and theophylline metabolite ratios were analyzed.

Main Results:

• Hemodynamic changes observed: increased heart rate in both phases; increased cardiac index with decreased diastolic blood pressure in the acute phase (p < 0.05).
• Theophylline plasma concentrations were slightly higher in the acute phase.
• Renal clearance of theophylline increased in the recovery phase (p < 0.05), and the urinary 3-methylxanthine to theophylline ratio was significantly higher in the acute phase (p < 0.05).

Conclusions:

• Theophylline administration affects hemodynamics differently in the acute and recovery phases post-cardiac surgery.
• Metabolism shifts towards N-demethylation, indicating partial activation of cytochrome P4501A2, rather than depression, in the immediate postoperative period.
• These findings highlight the dynamic changes in drug metabolism following cardiac surgery.