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Absolute bioavailability of theophylline from a sustained-release formulation using different intravenous reference
V W Steinijans1, H U Schulz, A Böhm
1Byk Gulden Research Centre, Konstanz, Federal Republic of Germany.
European Journal of Clinical Pharmacology
|January 1, 1987
Summary
This study investigated theophylline bioavailability using different intravenous infusion rates. Results suggest bioavailability may vary based on the chosen intravenous reference standard, impacting sustained-release formulation assessments.
Area of Science:
- Pharmacokinetics
- Drug Metabolism and Disposition
Background:
- Theophylline is a bronchodilator used for respiratory diseases.
- Sustained-release formulations aim for consistent drug levels.
- Accurate bioavailability assessment is crucial for therapeutic efficacy.
Purpose of the Study:
- To evaluate the impact of different intravenous infusion regimens on the absolute bioavailability of theophylline from a sustained-release oral formulation.
- To compare the bioavailability results obtained using two distinct intravenous aminophylline infusion protocols.
Main Methods:
- Oral administration of 750 mg theophylline (sustained-release) was compared to two intravenous aminophylline infusion studies.
- Study 1: 506 mg theophylline over 8 hours (63 mg/h).
- Study 2: 749 mg theophylline over 14 hours, with a rate reduction after 8 hours to mimic oral profiles.
Main Results:
- Absolute bioavailability was 100% (95% CI: 89-115%) in Study 1.
- Absolute bioavailability was 88% (95% CI: 73-105%) in Study 2.
- Lower clearance and bioavailability ratios were observed with the higher intravenous dose, though not statistically significant.
Conclusions:
- The choice of intravenous reference standard may influence the apparent absolute bioavailability of theophylline.
- This finding highlights the importance of selecting appropriate reference standards in pharmacokinetic studies.
- Further investigation is warranted to fully understand the relationship between infusion parameters and bioavailability outcomes.