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Delayed valproic acid toxicity: a retrospective case series.
Marianne Ingels1, Jon Beauchamp, Richard F Clark
1San Diego Division, California Poison Control System, San Diego, CA, USA.
Annals of Emergency Medicine
|May 23, 2002
Summary
Initial valproic acid (VPA) levels can be misleading in acute overdose cases. Delayed toxicity may occur, necessitating serial measurements or prolonged observation for safe patient discharge.
Area of Science:
- Clinical Toxicology
- Pharmacokinetics
- Emergency Medicine
Background:
- Valproic acid (VPA) overdose management relies on serum concentration monitoring.
- Initial VPA levels may not accurately reflect the full toxic potential due to delayed absorption.
Purpose of the Study:
- To determine the frequency of initially non-toxic or undetectable VPA concentrations in acute overdose cases.
- To assess the implications of initial VPA levels on predicting toxicity and guiding patient disposition.
Main Methods:
- Retrospective chart review of patients with serum VPA concentrations ≥120 µg/mL.
- Inclusion of cases with serial VPA measurements, including initial undetectable or <100 µg/mL levels.
- Analysis of decontamination, clinical outcomes, and VPA concentration trends.
Main Results:
- Of 173 patients with VPA ≥120 µg/mL, 21 (12.1%) had initial non-toxic levels and 5 (2.9%) had undetectable initial levels.
- These 26 cases involved acute VPA ingestion.
- Four patients were discharged prematurely based on initial results.
Conclusions:
- Initial serum VPA concentrations can be misleading in acute overdose.
- Delayed toxicity is possible, especially with enteric-coated formulations.
- Serial VPA monitoring and/or prolonged observation are crucial for safe management decisions.