Oxcarbazepine (Trileptal)
oxcarbazepine
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Partial-onset seizures | Adults | Monotherapy or adjunctive | FDA Approved |
| Partial-onset seizures | Children ≥4 years | Monotherapy | FDA Approved |
| Partial-onset seizures | Children ≥2 years | Adjunctive therapy | FDA Approved |
Oxcarbazepine is the 10-keto analogue of carbamazepine, sharing a similar sodium-channel-blocking mechanism but with important pharmacokinetic advantages: it does not undergo autoinduction, has fewer hepatic enzyme-inducing drug interactions, and avoids the problematic epoxide metabolite of carbamazepine. Oxcarbazepine is a prodrug rapidly converted to its active metabolite, the 10-monohydroxy derivative (MHD, also called licarbazepine), which mediates the therapeutic effect. It is a first-line option for focal-onset epilepsy in multiple international guidelines. Oxcarbazepine may aggravate primary generalised seizures, especially in children, and should be discontinued if seizure worsening occurs.
Trigeminal neuralgia — Used as an alternative to carbamazepine, particularly in patients intolerant to carbamazepine or requiring fewer drug interactions. Evidence quality: Moderate (RCTs showing comparable efficacy; recommended in AAN guidelines as an alternative).
Bipolar disorder — Used as a mood stabiliser; not FDA-approved for this indication. Evidence quality: Low (mixed evidence from small trials).
Dosing
Adult Dosing by Clinical Scenario
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Partial-onset seizures — adjunctive therapy | 600 mg/day (300 mg BID) | 1200 mg/day | 1200 mg/day (recommended); 2400 mg/day tolerated by some | Increase by max 600 mg/day weekly Most patients cannot tolerate 2400 mg/day, primarily due to CNS effects (FDA PI) |
| Partial-onset seizures — conversion to monotherapy | 600 mg/day (300 mg BID) | 2400 mg/day | 2400 mg/day | Withdraw concomitant AEDs over 3–6 weeks; reach max OXC dose in 2–4 weeks Increase by max 600 mg/day weekly |
| Partial-onset seizures — initiation of monotherapy | 600 mg/day (300 mg BID) | 1200 mg/day | 1200 mg/day (studied); 2400 mg/day (conversion data) | Increase by 300 mg/day every third day to 1200 mg/day |
| Renal impairment (CrCl <30 mL/min) | 300 mg/day (150 mg BID) | Titrate slowly based on response | Individualise | Start at half the usual starting dose MHD clearance reduced in renal impairment |
Pediatric Dosing
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Adjunctive — age 4–16 years | 8–10 mg/kg/day BID (max 600 mg/day start) | Weight-based: 20–29 kg: 900 mg/day; 29–39 kg: 1200 mg/day; >39 kg: 1800 mg/day | Weight-based (see maintenance) | Achieve target over 2 weeks |
| Adjunctive — age 2 to <4 years | 8–10 mg/kg/day BID (16–20 mg/kg/day if <20 kg) | Titrate over 2–4 weeks | 60 mg/kg/day | Young children may need up to 2× adult dose per kg Higher weight-normalised clearance in younger children |
| Monotherapy — age 4–16 years | 8–10 mg/kg/day BID | Weight-based per PI Table 1 (600–2100 mg/day) | Weight-based | Increase by 5 mg/kg/day every third day (initiation) or 10 mg/kg/day weekly (conversion) |
Unlike carbamazepine, oxcarbazepine does not induce its own metabolism. This means levels remain stable after initial titration without the need for dose readjustment at 3–5 weeks. It also means less enzyme induction overall, resulting in fewer drug-drug interactions — though oxcarbazepine is still a mild CYP3A4 and UGT inducer and will reduce levels of oral contraceptives, some AEDs, and other CYP3A4 substrates.
Pharmacology
Mechanism of Action
Oxcarbazepine is a prodrug that is rapidly and extensively reduced by cytosolic aryl ketone reductases to its pharmacologically active 10-monohydroxy derivative (MHD, licarbazepine). MHD blocks voltage-gated sodium channels in a use- and voltage-dependent manner, stabilising hyperexcited neuronal membranes, inhibiting repetitive neuronal firing, and diminishing propagation of synaptic impulses. MHD also modulates high-voltage-activated calcium channels and increases potassium conductance, contributing to neuronal membrane stabilisation. Additionally, oxcarbazepine and MHD inhibit the release of glutamate, which may contribute to anticonvulsant activity.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | OXC completely absorbed; rapidly converted to MHD (prodrug); food does not affect bioavailability; tabs and suspension are bioequivalent and interchangeable at equal doses | Can be taken with or without food; oral suspension and tablets can be substituted at equal doses |
| Distribution | MHD: Vd 49 L; ~40% bound to albumin (concentration-independent); OXC and MHD cross placenta and enter breast milk (milk:plasma ratio 0.5) | Lower protein binding than CBZ (~76%); less displacement interactions |
| Metabolism | OXC rapidly reduced by cytosolic enzymes to MHD (active); MHD glucuronidated via UGT; minor CYP involvement; NO autoinduction; mild CYP3A4 and CYP2C19 inhibitor; weak CYP3A4/UGT inducer | Far less enzyme induction than CBZ; no epoxide metabolite (avoiding CBZ-epoxide neurotoxicity); simpler drug interaction profile |
| Elimination | OXC t½ 1–3.7 h; MHD t½ 8–10 h; >95% excreted renally (primarily as MHD glucuronide); <1% OXC unchanged in urine | BID dosing sufficient for IR formulation; significant renal excretion — dose reduction needed for CrCl <30 mL/min; MHD levels may decline during pregnancy |
Side Effects
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Dizziness | 22–49% (dose-dependent; highest at 2400 mg/day adjunctive) | Most common reason for discontinuation (6.4%); dose-related; minimise by slow titration |
| Somnolence | 19–36% (dose-dependent) | Usually improves with continued therapy; higher with adjunctive use and in paediatric patients (35%) |
| Diplopia | 14–40% (dose-dependent) | Correlates with peak MHD levels; second most common cause of discontinuation (5.9%) |
| Nausea | 15–29% | Taking with food may help; typically transient |
| Vomiting | 13–36% | More common in paediatric patients; dose-related |
| Headache | 13–32% | Common across all trials; similar to placebo rates in some studies |
| Ataxia / abnormal gait | 10–31% | Dose-related; 23% in paediatric adjunctive trial (vs 7% placebo) |
| Adverse Effect | Incidence | Clinical Note |
|---|---|---|
| Fatigue | 5–9% | Usually dose-related and self-limiting |
| Tremor | 3–8% | Dose-related; differentiate from inadequate seizure control |
| Nystagmus | 5–7% | Sign of CNS toxicity at higher doses; may warrant dose reduction |
| Abnormal vision | 4–6% | Related to peak MHD concentrations |
| Rash | ~4% | Assess for SJS/TEN risk; 5.3% discontinuation rate in paediatric monotherapy initiation |
| Hyponatraemia (Na <125 mmol/L) | 2.5% (38/1524 in controlled trials; vs 0% placebo) | Usually first 3 months; most asymptomatic; monitor sodium levels; risk increased with diuretics and in elderly |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Clinically significant hyponatraemia | 2.5% (Na <125; vs 0% placebo/active control) | Usually first 3 months; may occur after >1 year | Monitor sodium during maintenance; consider discontinuation if symptomatic (nausea, confusion, lethargy, seizure worsening); normalises within days of stopping |
| SJS / TEN | 3–10× background rate; increased risk with HLA-B*1502 | Median 19 days; largely first few months | Consider HLA-B*1502 testing in at-risk populations (Asian ancestry); discontinue if skin reaction develops |
| Anaphylaxis / angioedema | Rare (postmarketing) | First or subsequent doses | Discontinue immediately; do not rechallenge |
| DRESS / Multiorgan hypersensitivity | Rare; some fatal | Days to weeks | Discontinue unless alternate aetiology established; presents with fever, rash, organ dysfunction |
| Cross-hypersensitivity with carbamazepine | 25–30% of CBZ-hypersensitive patients | Variable | Question all patients about prior CBZ reactions before starting; use only if benefit outweighs risk in CBZ-hypersensitive patients |
| Seizure aggravation | Reported, especially in children | Variable | Discontinue if primary generalised seizures worsen or new seizure types emerge |
| Suicidality (AED class effect) | 0.43% (vs 0.24% placebo) | As early as 1 week | Monitor for depression, suicidal thoughts, mood changes |
Hyponatraemia is the most distinctive safety concern with oxcarbazepine compared to carbamazepine. In the 14 controlled trials, 2.5% of patients developed sodium levels below 125 mmol/L (vs 0% with placebo or active comparators). Risk factors include older age, concomitant diuretics, and higher oxcarbazepine doses. Most cases are asymptomatic and occur in the first 3 months, but symptoms (confusion, lethargy, nausea, seizure worsening) can develop. Monitor sodium levels during maintenance, especially in elderly patients or those on drugs that lower sodium. Sodium normalises within days of dose reduction or discontinuation.
Drug Interactions
Oxcarbazepine has a simpler interaction profile than carbamazepine because it does not undergo autoinduction and is a weaker enzyme inducer. However, it is still a mild inducer of CYP3A4 and UGT enzymes, and it inhibits CYP2C19. The active metabolite MHD is primarily glucuronidated and renally excreted, so drugs that induce UGT or CYP3A4 can reduce MHD levels. The most clinically important interactions involve hormonal contraceptives, phenytoin, and concomitant enzyme-inducing AEDs.
Monitoring
- Serum SodiumBaseline, then during maintenance
RoutineHyponatraemia is the most clinically distinctive adverse effect of oxcarbazepine (2.5% had Na <125 in controlled trials vs 0% placebo). Usually occurs in the first 3 months but can develop later. Monitor more frequently in elderly, patients on diuretics, or those with symptoms (nausea, confusion, lethargy, seizure increase). Sodium normalises within days of discontinuation. - HLA-B*1502 TestingBefore initiation in at-risk populations
RoutineConsider testing in patients with ancestry in genetically at-risk Asian populations (Han Chinese, Filipino, Thai, Malaysian, Indian). The chemical structural similarity to carbamazepine and direct interaction data between OXC and HLA-B*1502 protein suggest increased SJS/TEN risk. Avoid OXC in HLA-B*1502 positive patients unless benefit clearly outweighs risk. - MHD LevelsIf clinically indicated
Trigger-basedRoutine TDM is not standard practice for oxcarbazepine. Consider measuring MHD levels in non-responders, suspected non-compliance, suspected drug interactions, pregnancy (MHD levels decline during pregnancy and may rebound postpartum), and renal impairment. Suggested therapeutic range for MHD: 3–35 mcg/mL (variable by lab). - Skin / RashFirst few months
RoutineSJS/TEN has been reported with OXC (reporting rate 3–10× background). Median onset 19 days. Counsel all patients to report any rash immediately; discontinue if serious skin reaction suspected. Cross-reactivity with CBZ: 25–30% of patients with prior CBZ hypersensitivity will react to OXC. - Seizure Control During PregnancyThroughout pregnancy and postpartum
RoutineMHD levels may gradually decrease during pregnancy due to physiological changes. Monitor closely and consider measuring MHD levels. Close monitoring should continue postpartum as MHD levels may rebound after delivery.
Contraindications & Cautions
Absolute Contraindications
- Known hypersensitivity to oxcarbazepine or any of its components
- Known hypersensitivity to eslicarbazepine acetate (structural analogue; cross-reactivity expected)
Relative Contraindications (Specialist Input Recommended)
- Prior hypersensitivity to carbamazepine — 25–30% cross-reactivity rate; use only if benefit clearly outweighs risk
- HLA-B*1502 positive patients — avoid unless benefit clearly outweighs risk of SJS/TEN
- Primary generalised epilepsies — may aggravate seizures, especially in children
Use with Caution
- Renal impairment (CrCl <30 mL/min) — start at half usual dose; MHD cleared renally
- Elderly patients — increased risk of hyponatraemia; start lower and titrate slowly
- Patients on diuretics or drugs that lower sodium — additive hyponatraemia risk
- Pregnancy — MHD levels decline during pregnancy; monitor seizure control closely
Serious dermatological reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, have been reported with oxcarbazepine. The reporting rate exceeds the background rate by a factor of 3 to 10-fold. The median time of onset was 19 days. The HLA-B*1502 allele, which increases the risk of SJS/TEN with carbamazepine, may also increase the risk with oxcarbazepine due to their structural similarity. Testing for HLA-B*1502 should be considered in patients with ancestry in genetically at-risk populations before initiating treatment. Oxcarbazepine should be avoided in HLA-B*1502 positive patients unless the benefits clearly outweigh the risks.
Patient Counselling
Purpose of Therapy
Oxcarbazepine helps control seizures by reducing abnormal electrical activity in the brain. It is taken regularly to prevent seizures from occurring and must be taken consistently for maximum benefit.
How to Take
Oxcarbazepine can be taken with or without food. The tablets and oral suspension deliver the same amount of drug and can be used interchangeably. Shake the oral suspension well before each use and measure with the supplied dosing syringe — do not use a household spoon. The suspension can be swallowed directly from the syringe or mixed in a small glass of water.
Sources
- Novartis Pharmaceuticals. TRILEPTAL (oxcarbazepine) prescribing information. Revised 09/2025. Reference ID: 5664343. FDA LabelPrimary regulatory source for all indications, dosing by clinical scenario, hyponatraemia data (2.5%, 38/1524), HLA-B*1502 guidance, and adverse reaction rates.
- Supernus Pharmaceuticals. OXTELLAR XR (oxcarbazepine extended-release) prescribing information. FDA LabelER formulation PI with once-daily dosing for adjunctive therapy in adults and children ≥6 years.
- Barcs G, Walker EB, Elger CE, et al. Oxcarbazepine placebo-controlled, dose-ranging trial in refractory partial epilepsy. Epilepsia. 2000;41(12):1597–1607. DOIPivotal dose-ranging trial establishing efficacy of adjunctive oxcarbazepine (600–2400 mg/day) in refractory partial epilepsy.
- Bill PA, Vigonius U, Pohlmann H, et al. A double-blind controlled clinical trial of oxcarbazepine versus phenytoin in adults with previously untreated epilepsy. Epilepsy Res. 1997;27(3):195–204. DOIHead-to-head monotherapy trial demonstrating comparable efficacy of oxcarbazepine and phenytoin in newly diagnosed epilepsy.
- Glauser TA, Nigro M, Sachdeo R, et al. Adjunctive therapy with oxcarbazepine in children with partial seizures. Neurology. 2000;54(12):2237–2244. DOIKey paediatric adjunctive trial providing adverse reaction data (somnolence 35%, ataxia 23%) used in the current PI.
- Glauser T, Ben-Menachem E, Bourgeois B, et al. Updated ILAE evidence review of antiepileptic drug efficacy and effectiveness as initial monotherapy for epileptic seizures and syndromes. Epilepsia. 2013;54(3):551–563. DOIILAE guideline supporting oxcarbazepine as a first-line option for focal seizures in adults and children.
- Kanner AM, Ashman E, Gloss D, et al. Practice guideline update summary: efficacy and tolerability of the new antiepileptic drugs I & II. Neurology. 2018;91(2):74–81. DOIAAN guideline update reviewing evidence for newer AEDs including oxcarbazepine as initial monotherapy for partial-onset seizures.
- Schütz H, Feldmann KF, Faigle JW, et al. The metabolism of 14C-oxcarbazepine in man. Xenobiotica. 1986;16(8):769–778. DOIOriginal metabolic study establishing the cytosolic reduction pathway from oxcarbazepine to MHD and confirming absence of epoxide metabolite.
- May TW, Korn-Merker E, Rambeck B. Clinical pharmacokinetics of oxcarbazepine. Clin Pharmacokinet. 2003;42(12):1023–1042. DOIComprehensive PK review covering MHD half-life (8–10 h), volume of distribution (49 L), protein binding (~40%), and renal clearance.
- Patsalos PN, Berry DJ, Bourgeois BFD, et al. Antiepileptic drugs — best practice guidelines for therapeutic drug monitoring. Epilepsia. 2008;49(7):1239–1276. DOIILAE TDM guideline providing MHD reference ranges and guidance on when to monitor levels.
- Preuss CV, Randhawa G, Saadabadi A. Oxcarbazepine. In: StatPearls. Treasure Island, FL: StatPearls Publishing; 2025. NCBIContinuously updated clinical summary covering indications, dosing, PK, and adverse effects including updated 2025 safety data.