Valproic Acid

Introduced 1978

Reviewed by the HeyPsych Medical Review Board

Board-certified psychiatrists and mental health professionals

Indications

Primary Indications

Epilepsy (generalized, focal, and absence seizures)Acute manic or mixed episodes in bipolar disorderMigraine prophylaxis

Mechanism

Increases GABA concentrations in the brain by inhibiting GABA degradation and enhancing synthesis; modulates voltage-gated sodium channels; inhibits T-type calcium channels.

Dosing

Adult Dosing

oral: Initial: 10–15 mg/kg/day in divided doses; increase by 5–10 mg/kg/week as needed to a usual range of 30–60 mg/kg/day (max 60 mg/kg/day). Adjust to achieve serum levels of 50–100 mcg/mL for epilepsy and 50–125 mcg/mL for mania.

Dosage Forms

Capsules: 250 mg
Oral solution: 250 mg/5 mL
Injection (IV): 100 mg/mL

Onset Duration

Seizure control may be seen within days; mood stabilization may take 1–2 weeks; migraine prophylaxis may require several weeks.

Adverse Effects

Common Side Effects

• nausea

• vomiting

• tremor

• weight gain

• hair loss

• somnolence

⚠️ Serious Side Effects

hepatotoxicity
pancreatitis
hyperammonemia
thrombocytopenia
teratogenicity

Warnings

Critical Safety Information

→Black box warning: hepatotoxicity, especially in children under 2 years
→Black box warning: teratogenicity—contraindicated in pregnancy for migraine prophylaxis
→Risk of pancreatitis—discontinue if suspected
→May increase ammonia levels—monitor especially if lethargy or vomiting occur

Interactions

With: Lamotrigine

Risk: Increased lamotrigine concentration and risk of rash

Action: Reduce lamotrigine dose

With: Carbamazepine

Risk: Altered levels of both drugs

Action: Monitor and adjust

With: Aspirin

Risk: Increased free valproic acid levels

Action: Monitor for toxicity

Monitoring

Liver function tests
CBC with platelets
Serum valproic acid level
Serum ammonia if indicated

Special Populations

👶Pregnancy

Contraindicated for migraine prophylaxis; for epilepsy or bipolar disorder, use only if no alternatives are suitable due to high teratogenic risk

🤱Breastfeeding

Excreted in breast milk; use with caution and monitor infant

👴Older Adults (65+)

Use lowest effective dose; monitor for sedation and hepatotoxicity

Tapering

Gradual dose reduction over weeks is recommended to reduce the risk of seizure recurrence or mood relapse.

Clinical Notes

Therapeutic serum range: 50–100 mcg/mL for epilepsy; 50–125 mcg/mL for mania
Valproic acid is more rapidly absorbed than valproate sodium, which may influence tolerability
Available in oral and IV forms for acute or maintenance therapy

This medication information is for educational purposes only and is not a substitute for professional medical advice. Always consult your healthcare provider before starting, stopping, or changing any medication. Never take medication without a prescription from a licensed healthcare provider.

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