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A double Weibull input function describes the complex absorption of sustained-release oral sodium valproate
F Bressolle1, R Gomeni, R Alric
1Département de Pharmacocinétique, Faculté de Pharmacie, Montpellier, France.
Journal of Pharmaceutical Sciences
|October 1, 1994
Summary
This study modeled valproic acid pharmacokinetics using Weibull functions in healthy volunteers. A double Weibull model best described the complex drug absorption, revealing key parameters for sustained-release formulations.
Area of Science:
- Pharmacokinetics
- Mathematical Modeling
- Drug Formulation
Background:
- Valproic acid is used for various conditions.
- Understanding its pharmacokinetics is crucial for effective dosing.
- Sustained-release formulations aim for consistent drug levels.
Purpose of the Study:
- To develop a mathematical model for valproic acid's complex oral absorption.
- To analyze the double peak phenomenon observed in plasma concentrations.
- To evaluate the suitability of Weibull functions for describing drug intake.
Main Methods:
- Studied 12 healthy volunteers orally administered sustained-release valproic acid.
- Measured plasma valproic acid concentrations using High-Performance Liquid Chromatography (HPLC).
- Fitted plasma concentration data using single or double Weibull input functions and first-order elimination.
Main Results:
- A double peak phenomenon in plasma concentration was observed in most subjects.
- A double Weibull input function provided a better fit for nine subjects.
- Mean peak plasma concentration was 34.6 mg/L at 8.6 hours; mean half-life was 14.4 hours.
Conclusions:
- The Weibull model approximates the complex oral drug intake process of valproic acid.
- The double Weibull function is more appropriate for describing the observed absorption profiles.
- Findings provide insights into optimizing sustained-release valproic acid formulations.