Most valproate overdoses result in CNS depression and are managed successfully with supportive care. Large overdoses can cause multiple organ failure and death. Death is preventable with early haemodialysis.
| Dose | Effect |
| < 200 mg/kg | Asymptomatic, or mild drowsiness and ataxia only |
| 200–400 mg/kg | Variable CNS depression; airway control rarely required |
| 400 –1000 mg/kg | Significant CNS depression likely Coma requiring intubation may be delayed up to 12 hours after ingestion. As doses increase within this range, more severe multi-system toxicity is observed |
| >1000 mg/kg | Potentially lethal with profound prolonged coma and multiple organ toxicity, including cerebral oedema, hypotension, lactic acidosis, hypoglycaemia, hyperammonaemia, hypernatraemia, hypocalcaemia and bone marrow suppression |
References
- Isbister GK, Balit CR, Whyte IM et al. Valproate overdose: a comparative cohort study of self-poisonings. British Journal of Clinical Pharmacology 2003; 55:398-404.
- Sztajnkrycer MD. Valproic acid toxicity: Overview and management. Journal of Toxicology – Clinical Toxicology 2002; 40(6):789-801.
- Spiller HA, Krenzelok EP, Klein-Schwartz W et al. Multicenter case series of valproic acid ingestion: serum concentrations and toxicity. Clinical Toxicology 2000; 38(7):755-760.
- Thanacoody RH. Extracorporeal elimination in acute valproic acid poisoning. Clinical Toxicology 2009; 47(7):609-616.
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