VALPROATE SODIUM

Clinical safety rating: caution

Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).

How it works

Increases GABA levels by inhibiting GABA transaminase and blocking voltage-gated sodium channels; also modulates T-type calcium channels.

What the body does with it

Metabolism	Extensively metabolized in the liver via glucuronidation and beta-oxidation; minor CYP450 involvement; some metabolites are pharmacologically active.
Excretion	Primarily renal (90% as glucuronide conjugates, 3-oxo derivative, and other metabolites; <3% unchanged). Biliary/fecal excretion accounts for <10%.
Half-life	Terminal elimination half-life is 9–16 hours in adults; may be shorter in children (5–12 hours) and prolonged in hepatic impairment or elderly (up to 18 hours). Neonatal half-life: 10–67 hours. Clinically, twice-daily dosing is typical.
Protein binding	90% bound, primarily to albumin; binding is concentration-dependent and saturable at higher concentrations.
Volume of Distribution	0.13–0.23 L/kg; clinically, distributes mainly into plasma and extracellular fluid, with limited CNS penetration (CSF levels 10% of plasma).
Bioavailability	Oral (divalproex sodium): nearly 100% (delayed release); IV: 100%. Extended-release: 90% relative to delayed-release.
Onset of Action	Oral: 1–4 hours (delayed due to enteric coating; liquid/IV: within minutes). IV loading: within 15 minutes for seizure control.
Duration of Action	Oral (divalproex): 12–24 hours (serum levels maintained); IV: 6–8 hours post-loading for acute effects. Chronic therapy has prolonged action due to accumulation.

Classification & Brands

Dosing & administration

10-15 mg/kg/day orally or intravenously in 2-3 divided doses; increase by 5-10 mg/kg/day weekly to therapeutic range of 50-100 mcg/mL. Maximum dose 60 mg/kg/day.

Dosage form	INJECTABLE
Renal impairment	No adjustment needed for GFR >10 mL/min; for GFR <10 mL/min, reduce dose by 25% and monitor free valproate levels due to decreased protein binding.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% and monitor liver function. Child-Pugh C: contraindicated.
Pediatric use	10-15 mg/kg/day divided 2-3 times daily; titrate upward by 5-10 mg/kg/day weekly. Maximum recommended dose 60 mg/kg/day. For children less than 20 kg, use starting dose 15-20 mg/kg/day.
Geriatric use	Start at lower end of dosing (10 mg/kg/day) and titrate slowly; monitor for increased free fractions due to hypoalbuminemia; target trough levels 50-100 mcg/mL; avoid use in patients with dementia due to increased risk of adverse effects.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).

Breastfeeding	Valproate is excreted into breast milk at low levels; M/P ratio ~0.05-0.1. Infant plasma levels are 1-6% of maternal levels. Although considered compatible with breastfeeding by most authorities, monitor infant for thrombocytopenia, hepatic dysfunction, and sedation.
Teratogenic Risk	First trimester: Major congenital malformations (neural tube defects, cardiac, orofacial clefts) in 3-5% of exposed fetuses; risk increased with doses >1000 mg/day. Second and third trimesters: Fetal growth restriction, neurodevelopmental deficits, neonatal withdrawal syndrome. All trimesters: Risk of hemorrhage due to fetal coagulopathy.

Warnings & precautions

■ FDA Black Box Warning

Hepatotoxicity, especially in children under 2 years, those with congenital metabolic disorders, severe seizure disorders with mental retardation, or organic brain disease; teratogenicity, including neural tube defects; pancreatitis.

Side Effect Profile

Serious Effects

Absolute Contraindications

Hepatic disease or significant hepatic dysfunction; known mitochondrial disorders (e.g., Alpers-Huttenlocher syndrome); hypersensitivity to valproate; urea cycle disorders; pregnancy (for migraine prophylaxis) or in women of childbearing potential unless essential.

Clinical Precautions

Precautions

Hepatotoxicity; pancreatitis; teratogenicity; hyperammonemic encephalopathy; thrombocytopenia; hypothermia; multiorgan hypersensitivity reactions; valproate can cause decreased bone mineral density; monitoring of liver function, platelet count, and ammonia levels recommended.

Clinical Tips & Counseling

Drug interactions

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VALPROATE SODIUM

Clinical safety rating: caution

Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).

How it works

Increases GABA levels by inhibiting GABA transaminase and blocking voltage-gated sodium channels; also modulates T-type calcium channels.

What the body does with it

Metabolism	Extensively metabolized in the liver via glucuronidation and beta-oxidation; minor CYP450 involvement; some metabolites are pharmacologically active.
Excretion	Primarily renal (90% as glucuronide conjugates, 3-oxo derivative, and other metabolites; <3% unchanged). Biliary/fecal excretion accounts for <10%.
Half-life	Terminal elimination half-life is 9–16 hours in adults; may be shorter in children (5–12 hours) and prolonged in hepatic impairment or elderly (up to 18 hours). Neonatal half-life: 10–67 hours. Clinically, twice-daily dosing is typical.
Protein binding	90% bound, primarily to albumin; binding is concentration-dependent and saturable at higher concentrations.
Volume of Distribution	0.13–0.23 L/kg; clinically, distributes mainly into plasma and extracellular fluid, with limited CNS penetration (CSF levels 10% of plasma).
Bioavailability	Oral (divalproex sodium): nearly 100% (delayed release); IV: 100%. Extended-release: 90% relative to delayed-release.
Onset of Action	Oral: 1–4 hours (delayed due to enteric coating; liquid/IV: within minutes). IV loading: within 15 minutes for seizure control.
Duration of Action	Oral (divalproex): 12–24 hours (serum levels maintained); IV: 6–8 hours post-loading for acute effects. Chronic therapy has prolonged action due to accumulation.

Classification & Brands

Dosing & administration

10-15 mg/kg/day orally or intravenously in 2-3 divided doses; increase by 5-10 mg/kg/day weekly to therapeutic range of 50-100 mcg/mL. Maximum dose 60 mg/kg/day.

Dosage form	INJECTABLE
Renal impairment	No adjustment needed for GFR >10 mL/min; for GFR <10 mL/min, reduce dose by 25% and monitor free valproate levels due to decreased protein binding.
Liver impairment	Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50% and monitor liver function. Child-Pugh C: contraindicated.
Pediatric use	10-15 mg/kg/day divided 2-3 times daily; titrate upward by 5-10 mg/kg/day weekly. Maximum recommended dose 60 mg/kg/day. For children less than 20 kg, use starting dose 15-20 mg/kg/day.
Geriatric use	Start at lower end of dosing (10 mg/kg/day) and titrate slowly; monitor for increased free fractions due to hypoalbuminemia; target trough levels 50-100 mcg/mL; avoid use in patients with dementia due to increased risk of adverse effects.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).

Breastfeeding	Valproate is excreted into breast milk at low levels; M/P ratio ~0.05-0.1. Infant plasma levels are 1-6% of maternal levels. Although considered compatible with breastfeeding by most authorities, monitor infant for thrombocytopenia, hepatic dysfunction, and sedation.
Teratogenic Risk	First trimester: Major congenital malformations (neural tube defects, cardiac, orofacial clefts) in 3-5% of exposed fetuses; risk increased with doses >1000 mg/day. Second and third trimesters: Fetal growth restriction, neurodevelopmental deficits, neonatal withdrawal syndrome. All trimesters: Risk of hemorrhage due to fetal coagulopathy.