oxcarbazepine

General Information

Carbamazepine analog used off-label as an alternative mood stabilizer when carbamazepine is effective but poorly tolerated, offering fewer CYP450 interactions yet higher hyponatremia risk.

Guidelines rank oxcarbazepine as third-line for acute mania or adjunctive maintenance, underscoring the need for careful patient selection and monitoring.

The contrast view and the Oxcarbazepine evidence feed help contextualize dosing, interactions, and sodium risk relative to first-line agents.

Often considered when carbamazepine interactions or hematologic toxicity limit use; sodium monitoring and hyponatremia education often become central follow-up tasks.

Mechanism of Action

Refer to the Glossary entry on Neurotransmitters for background on receptor systems involved in serious mental illness.

Blocks voltage-dependent sodium channels via active monohydroxy derivative (MHD), stabilizing hyperexcitable neuronal membranes and reducing glutamate release.

• Primary mechanism is sodium-channel blockade; ancillary modulation of calcium currents may contribute to mood stabilization.

Metabolism and Pharmacokinetics

• Rapidly reduced to active MHD; IR Tmax 4–6 h, XR Tmax ~7 h with food.
• MHD ~40% protein bound; half-life ~9 h (extends to ~17 h in severe renal impairment).
• Predominantly eliminated renally as glucuronide conjugates (~95% of dose), with <1% excreted unchanged.

Dosing and Administration

• Acute mania: start 300 mg twice daily (IR); increase by 300 mg/day every 3–4 days to 900–1,200 mg/day, with experience limited above 1,800 mg/day in psychiatric populations.
• Oxtellar XR: initiate 600 mg once nightly with food; titrate by 600 mg weekly to 1,200–2,400 mg nightly.
• Cross-taper from carbamazepine at ~1.5× equivalent dose while tapering carbamazepine over one week.
• CrCl <30 mL/min: start at half the usual dose (e.g., 150 mg BID IR) and titrate slowly with sodium monitoring.
• Taper by ~300 mg/week (or 10%) to discontinue, extending longer if seizure threshold concerns arise.

Monitoring & Labs

• Serum sodium at baseline and during titration (and after dose or medication changes), given high hyponatremia risk.
• Neurologic tolerability (dizziness, diplopia, ataxia) during titration; these symptoms often appear before clinically significant hyponatremia.
• Medication review for additive sodium-lowering agents (SSRIs, thiazides, desmopressin) and for contraceptive efficacy given CYP3A4/UGT induction.
• Rash or mucosal symptoms during early therapy; cross-reactivity with prior carbamazepine rash can occur and warrants heightened vigilance.
• Bone health for long-term therapy (vitamin D, calcium, and fall risk), especially in older adults or when other enzyme-inducing medications are used.

Oxcarbazepine is often chosen to reduce carbamazepine’s interaction burden, but sodium monitoring becomes the dominant follow-up task in many patients. Education typically covers fatigue, confusion, headache, and falls as potential hyponatremia signals, and sodium is often rechecked promptly when symptoms arise. Contraception plans may need review when pregnancy is possible because CYP3A4/UGT induction can lower hormonal contraceptive efficacy.

Adverse Effects

Interactions

• Induces CYP3A4/UGT, reducing efficacy of hormonal contraceptives, some antipsychotics, and antiretrovirals—backup or non-hormonal contraception is commonly discussed.
• Inhibits CYP2C19, increasing phenytoin concentrations; phenytoin levels may rise, so monitoring and dose adjustment may be needed.
• Additive hyponatremia with SSRIs, thiazide diuretics, carbamazepine, or desmopressin; this may warrant closer sodium monitoring.
• CNS depressants (alcohol, benzodiazepines) potentiate dizziness and sedation.

Other Useful Information

• Education typically covers hyponatremia symptoms (fatigue, confusion, seizures) and when urgent evaluation is needed.
• HLA-B*1502 screening is often discussed for at-risk ancestry, especially with prior carbamazepine reactions.
• Pregnancy registry enrollment and folate supplementation are commonly discussed; MHD transfers to breast milk.
• Integrate relapse planning with the bipolar disorder hub when oxcarbazepine augments or replaces first-line mood stabilizers.
• Abrupt discontinuation is typically avoided when possible; tapering helps prevent rebound seizures (in epilepsy) and mood destabilization (in bipolar disorder).

References

1. TRILEPTAL (oxcarbazepine) prescribing information — DailyMed (2025)
2. Oxtellar XR prescribing information — DailyMed (2025)
3. The CANMAT and ISBD Guidelines for the Management of Patients With Bipolar Disorder: 2021 Update — Bipolar Disorders (2021)Guidelinebipolarclinical
4. Clinical Review: Oxcarbazepine Induced Hyponatremia — Epilepsy & Behavior (2015)