OXCARBAZEPINE EXTENDED RELEASE TABLETS
Clinical safety rating: caution
Strong CYP3A4 inducers may decrease levels of active metabolite Can cause hyponatremia and cross-hypersensitivity with carbamazepine.
Stabilizes neuronal membranes by blocking voltage-sensitive sodium channels, inhibiting repetitive firing of action potentials, and reducing the propagation of synaptic impulses. Also modulates calcium channels and enhances potassium conductance.
| Metabolism | Extensively metabolized by cytosolic enzymes (not CYP450) to active 10-monohydroxy derivative (MHD). MHD is further conjugated with glucuronic acid; minor CYP450 involvement (CYP3A4/5). |
| Excretion | Renal: ~70% (mainly as glucuronide conjugates of MHD and oxcarbazepine, with <1% unchanged oxcarbazepine and ~27% unchanged MHD). Fecal: <1%. |
| Half-life | Oxcarbazepine: ~2 hours (not clinically relevant due to rapid conversion to MHD). MHD: ~9 hours (steady-state achieved in 2-3 days). |
| Protein binding | Oxcarbazepine: ~60% (primarily to albumin). MHD: ~40% (primarily to albumin). |
| Volume of Distribution | Oxcarbazepine: 1.3 L/kg. MHD: 0.8 L/kg. Suggests extensive tissue distribution. |
| Bioavailability | Extended-release tablets: ~85% relative to immediate-release, with 20% lower peak but equivalent AUC. |
| Onset of Action | Extended-release tablets: 3-4 hours after single dose for MHD peak; therapeutic effect within 1-2 weeks of regular dosing. |
| Duration of Action | Extended-release tablets: 12-hour dosing interval for seizure control, with trough levels maintained within therapeutic range (MHD 12-30 mg/L). |
| Molecular Weight | 252.27 |
Initial: 300 mg orally twice daily. Increase by up to 600 mg/day at weekly intervals. Target maintenance: 1200-2400 mg/day in two divided doses. Extended-release tablets are dosed once daily: initial 600 mg, titrate weekly by 600 mg to maintenance 1200-2400 mg once daily.
| Dosage form | TABLET |
| Renal impairment | For CrCl <30 mL/min: initiate at 150 mg twice daily (or 300 mg once daily for extended-release) and titrate slowly. Hemodialysis: reduce dose by 50% and administer after dialysis session. |
| Liver impairment | No specific guidelines for Child-Pugh. Use with caution in severe impairment; consider starting at 150 mg twice daily and monitor. |
| Pediatric use | Age 2-16 years: initial 8-10 mg/kg/day in two divided doses (max 600 mg/day) for immediate-release. Extended-release: not approved for children <6 years; for 6-16 years: initial 8-10 mg/kg once daily (max 600 mg), titrate weekly by 8-10 mg/kg (max 600 mg increase) to target 20-30 mg/kg once daily (max 2400 mg/day). |
| Geriatric use | Initiate at 150 mg twice daily (immediate-release) or 300 mg once daily (extended-release). Titrate slowly with close monitoring for hyponatremia and neurological adverse effects. Consider lower target doses. |
| 1st trimester | Increased risk of major congenital malformations (e.g., neural tube defects, facial clefts). Folic acid supplementation recommended; consider alternative therapy if possible. |
| 2nd trimester | Monitor for adverse effects; increased clearance may require dose adjustment. Risk of fetal hemorrhage if maternal vitamin K deficiency. |
| 3rd trimester | Risk of neonatal hemorrhage (vitamin K deficiency), sedation, and withdrawal symptoms. Supplement vitamin K in mother during last month. |
Clinical note
Strong CYP3A4 inducers may decrease levels of active metabolite Can cause hyponatremia and cross-hypersensitivity with carbamazepine.
| FDA category | Animal |
| Placental transfer | Crosses placenta readily; cord blood levels similar to maternal levels. |
■ FDA Black Box Warning
None
| Common Effects | Headache Nausea Vomiting Fatigue Dizziness Nystagmus involuntary eye movement Tremors Vertigo Drowsiness Abnormality of voluntary movements Abnormal gait Visual disturbance Increased sodium level in blood |
| Serious Effects |
Hypersensitivity to oxcarbazepine or any componentKnown severe allergic reaction to carbamazepineHypersensitivity to eslicarbazepine
| Precautions | Cross-sensitivity with carbamazepine (about 25-30% hypersensitivity risk), Risk of hyponatremia (monitor sodium levels, especially in elderly or patients with renal impairment), Increased risk of suicidal thoughts or behavior, Dizziness and somnolence (caution with machinery operation), Withdrawal seizures (do not abruptly discontinue), Dermatological reactions (SJS/TEN; discontinue if rash develops), Hematologic effects (rare agranulocytosis; monitor if symptoms of infection) |
| Food/Dietary |
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| Breastfeeding |
| Excreted in breast milk; infant serum levels low. Monitor infant for drowsiness, poor feeding, and rash. Generally compatible with caution. |
| Lactation Rating | L3 (Moderately Safe) |
| Teratogenic Risk | Increases risk of major congenital malformations, particularly neural tube defects (e.g., spina bifida), craniofacial defects, and cardiac anomalies, with first-trimester exposure. Second- and third-trimester exposure may be associated with decreased fetal growth, neurodevelopmental issues, and neonatal hemorrhage due to vitamin K deficiency. |
| Fetal Monitoring | Monitor maternal serum drug levels (total and free MHD) every trimester and post-delivery; adjust dose to maintain therapeutic levels (MHD trough 10-35 mcg/mL). Perform fetal ultrasound in second trimester for structural anomalies. Assess fetal growth by serial ultrasounds. Measure maternal folate levels and supplement with 4-5 mg/day folic acid preconception and during first trimester. Monitor neonatal for coagulopathy with vitamin K administration at delivery. |
| Fertility Effects | No direct evidence of impaired fertility in humans. Animal studies show no adverse effects on fertility. May induce hepatic enzymes affecting sex hormone metabolism; use of effective contraception is advised in women of reproductive potential due to teratogenicity. |
| Grapefruit and grapefruit juice may increase oxcarbazepine levels; avoid concurrent use. Alcohol enhances CNS depression; limit or avoid. No significant food effect on absorption; can be taken with or without food. |
| Clinical Pearls | Oxcarbazepine ER is dosed once daily; titrate slowly to minimize CNS side effects like dizziness and somnolence. Monitor serum sodium due to risk of hyponatremia, especially in elderly or patients on diuretics. No significant hematologic monitoring required unlike carbamazepine. Autoinduction not significant; dose adjustments may be needed with renal impairment (CrCl <30 mL/min). Contraindicated in patients with known hypersensitivity to carbamazepine (cross-reactivity ~25%). |
| Patient Advice | Take this medication once daily at the same time each day; do not crush, chew, or split the extended-release tablet. · Avoid abrupt discontinuation; seizure frequency may increase. Taper under medical supervision. · Report signs of hyponatremia: nausea, headache, confusion, weakness, or seizures. · Do not drive or operate machinery until you know how this medicine affects you; dizziness and drowsiness are common. · Inform your doctor if you are pregnant, planning pregnancy, or breastfeeding; this drug may reduce effectiveness of oral contraceptives. · Limit alcohol intake; may increase CNS side effects. |