Pharmacokinetic interactions between theophylline and rioprostil

Area of Science:

• Pharmacology
• Clinical Pharmacy

Background:

• Theophylline is a widely used bronchodilator with a narrow therapeutic index.
• Drug interactions can alter theophylline's pharmacokinetic profile, necessitating dose adjustments.
• Rioprostil, a prostaglandin E1 analogue, has been investigated for various therapeutic applications.

Purpose of the Study:

• To investigate the effect of rioprostil on the pharmacokinetics of slow-release theophylline in healthy volunteers.
• To determine if co-administration of rioprostil requires changes in theophylline dosage.

Main Methods:

• Double-blind, placebo-controlled, crossover study design.
• Eight healthy male volunteers participated.
• Slow-release theophylline doses were adjusted to achieve steady-state plasma levels (200 mg or 400 mg twice daily).
• Pharmacokinetic parameters were assessed during one-week treatment periods with either rioprostil (300 µg twice daily) or placebo.

Main Results:

• Side effects were observed and attributed to theophylline administration, appearing before day 6.
• Steady-state plasma theophylline concentrations were verified.
• No significant differences in mean pharmacokinetic parameters were found when slow-release theophylline was administered alone or with rioprostil.

Conclusions:

• Rioprostil does not significantly alter the pharmacokinetics of slow-release theophylline.
• Theophylline dosage does not require adjustment when prescribed concurrently with rioprostil.
• These findings have clinical relevance for managing patients on both medications.