Related Experiment Videos
Disposition of valproic acid in man
European Journal of Clinical Pharmacology
|October 14, 1977
Summary
This study on valproic acid (VPA) pharmacokinetics in healthy subjects found consistent absorption and elimination. Steady-state plasma concentrations were lower than predicted, likely due to reduced protein binding at higher VPA levels.
Area of Science:
- Pharmacology
- Clinical Pharmacy
- Drug Metabolism
Background:
- Valproic acid (VPA) is a widely used antiepileptic drug.
- Understanding its pharmacokinetic profile is crucial for optimizing therapeutic efficacy and minimizing adverse effects.
Purpose of the Study:
- To investigate the pharmacokinetics of valproic acid (VPA) in healthy subjects after single and multiple doses.
- To evaluate absorption, distribution, metabolism, and excretion (ADME) parameters of VPA.
Main Methods:
- A single 600 mg dose and multiple daily doses (1200 mg) of enteric-coated sodium valproate were administered to 6 healthy subjects over 12 days.
- Plasma and saliva concentrations of VPA were measured.
- Pharmacokinetic parameters including half-life, clearance, volume of distribution, and steady-state concentration (Css) were calculated.
Main Results:
- VPA exhibited a 1-2 hour absorption lag time, followed by rapid absorption with peak concentrations at 3-4 hours.
- The terminal half-life was approximately 16-17 hours, with no evidence of dose-dependent kinetics or autoinduction.
- Observed Css was lower than predicted, attributed to reduced plasma protein binding at higher concentrations.
- Urinary excretion included 3.2% parent drug and 21.2% conjugated metabolites.
Conclusions:
- Valproic acid demonstrates predictable pharmacokinetics with a moderate half-life and low volume of distribution.
- Reduced plasma protein binding at higher concentrations influences steady-state levels.
- Saliva VPA concentrations do not accurately reflect unbound plasma drug levels.