Absolute bioavailability of oral theophylline

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Drug Delivery Systems

Background:

• Theophylline is a bronchodilator used for asthma management.
• Understanding the bioavailability of different theophylline formulations is crucial for effective treatment.
• Previous studies have indicated good oral absorption of theophylline, but direct comparisons of tablet and solution forms are valuable.

Purpose of the Study:

• To determine and compare the absolute bioavailability of an anhydrous theophylline tablet and a theophylline solution.
• To assess the rate and extent of absorption for both oral formulations in adult asthmatic patients.

Main Methods:

• A crossover study design was employed with 20 adult asthmatic patients.
• Patients received intravenous theophylline, followed by either an oral tablet or solution in a separate period.
• Serum theophylline concentrations were measured using high-pressure cation exchange chromatography over 12 hours.

Main Results:

• The mean fraction of the dose absorbed was 0.96 ± 0.03 for the tablet and 0.99 ± 0.02 for the solution.
• Peak serum concentrations were achieved at approximately 2 hours for tablets and 1.4 hours for solutions.
• Absorption of both theophylline tablets and solutions approached 100% of the available drug.

Conclusions:

• Both the tested theophylline tablet and solution demonstrate high absolute bioavailability, approaching complete absorption.
• The findings support the use of these oral theophylline formulations for effective drug delivery in asthma patients.
• Minor differences in peak absorption time were observed between the tablet and solution forms.