VALPROATE SODIUM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).
Increases GABA levels by inhibiting GABA transaminase and blocking voltage-gated sodium channels; also modulates T-type calcium channels.
| 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. |
| Molecular Weight | 166.17 |
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. |
| 1st trimester | High risk of neural tube defects and other major congenital malformations. Avoid use unless no alternative. Consider folate supplementation. |
| 2nd trimester | Associated with fetal anomalies and neurodevelopmental disorders. Use only if clearly needed and benefits outweigh risks. |
| 3rd trimester | Risk of neonatal hemorrhage, hepatotoxicity, and withdrawal symptoms. Monitor coagulation and liver function in neonate. |
Clinical note
Comprehensive clinical and safety monograph for VALPROATE SODIUM (VALPROATE SODIUM).
| Placental transfer | Crosses placenta freely. Cord blood concentrations approximate maternal serum levels. Fetal exposure is significant. |
| Breastfeeding | Valproate is excreted into breast milk in low concentrations (1-10% of maternal serum levels). Monitor infant for drowsiness, poor feeding, and hepatic dysfunction. Caution is advised, but benefit of breastfeeding may outweigh risks if maternal therapy is essential. |
■ 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.
| Serious Effects |
Liver diseaseSignificant hepatic dysfunctionUrea cycle disordersKnown hypersensitivity to valproatePorphyria
| 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. |
| Food/Dietary | No significant food interactions. Valproate can be taken with or without food; however, administration with food may reduce gastrointestinal upset. Avoid ethanol due to increased sedation and hepatotoxicity risk. |
Loading safety data…
| Lactation Rating | L3 (Moderately Safe) |
| 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. |
| Fetal Monitoring | Preconception: Ensure folate supplementation (5 mg/day). First trimester: Ultrasound for neural tube defects, echocardiography by 18-22 weeks. Throughout pregnancy: Serial fetal growth scans. Neonatal: Monitor for coagulopathy (vitamin K prophylaxis recommended), withdrawal symptoms, and hepatotoxicity. |
| Fertility Effects | Associated with polycystic ovary syndrome (PCOS) in some women, potentially causing anovulatory cycles and impaired fertility. In men, reversible oligospermia and reduced sperm motility have been reported. |
| Clinical Pearls | Valproate sodium has a narrow therapeutic index (50-100 mcg/mL). Trough levels 12 hours post-dose are recommended. Avoid in women of childbearing potential due to teratogenicity (neural tube defects). Monitor for hyperammonemia, especially in patients with urea cycle disorders. Thrombocytopenia occurs at high doses. For IV push, administer over 5-10 minutes (max 20 mg/min). Do not crush enteric-coated tablets. Valproate is a broad-spectrum AED effective for both generalized and partial seizures, and is first-line for idiopathic generalized epilepsies. |
| Patient Advice | Take exactly as prescribed; do not stop abruptly as this may cause seizures. · Report any signs of liver problems: nausea, vomiting, abdominal pain, jaundice, or fatigue. · Women of childbearing age must use effective contraception due to risk of birth defects. · Avoid alcohol while taking this medication. · Do not drive until you know how this medication affects you; may cause dizziness or drowsiness. · Swallow tablets whole; do not crush or chew enteric-coated tablets. · Keep all appointments for blood tests to monitor drug levels and liver function. · If you miss a dose, take it as soon as you remember unless it's close to next dose; do not double dose. · Report unusual bruising or bleeding (signs of thrombocytopenia). · Inform all healthcare providers you are taking valproate before any surgery. |