oxcarbazepine
Brand: Trileptal, Oxtellar XR
TDM Required Prototype: carbamazepine
Drug Class: antiepileptic drug
Drug Family: antiepileptic
Subclass: voltage-gated Na+ channel blocker (carbamazepine analog)
Organ Systems: cns
Mechanism of Action
Active 10-monohydroxy metabolite (MHD) blocks voltage-gated Na+ channels in a use-dependent manner, reducing repetitive neuronal firing. No CYP autoinduction (unlike carbamazepine) and produces fewer CYP-mediated drug interactions.
voltage-gated sodium channels (Nav)
Indications
- partial (focal) seizures (monotherapy and adjunctive therapy)
- bipolar disorder (off-label)
Contraindications
- hypersensitivity to carbamazepine (25–30% cross-reactivity)
Adverse Effects
Common
- dizziness
- somnolence
- diplopia
- nausea
- headache
- ataxia
Serious
- hyponatremia (more common than carbamazepine — up to 25%)
- SJS/TEN (lower risk than carbamazepine; may still occur in HLA-B*1502 carriers)
- aplastic anemia (less common than carbamazepine)
- teratogenicity
Pharmacokinetics (ADME)
| Absorption | oral; bioavailability >95% as the active MHD metabolite |
| Distribution | 40% protein bound (MHD) |
| Metabolism | hepatic; reduced to MHD (primary active metabolite); no epoxide formation |
| Excretion | renal (>95%) |
| Half-life | 9–11 hours (MHD) |
| Onset | days |
| Peak | 4–6 hours (MHD) |
| Duration | continuous |
| Protein Binding | 40% |
| Vd | 0.7 L/kg (MHD) |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| oral contraceptives | mild CYP3A4 induction reduces OCP levels; additional contraception advised | major |
| carbamazepine | increased carbamazepine toxicity due to metabolic interactions | moderate |
| verapamil | CYP3A4 induction by oxcarbazepine may reduce verapamil levels | moderate |
Nursing Considerations
- Monitor serum sodium levels; hyponatremia is frequent (up to 25% of patients) and may be symptomatic; particularly monitor in elderly and in patients taking diuretics.
- Lower risk of drug interactions than carbamazepine, but patients still need additional contraception methods (enzyme induction reduces OCP efficacy).
- Cross-reactivity with carbamazepine rash is 25–30%; do not use as substitution without careful evaluation in patients with carbamazepine skin reactions.
- No need for CBC monitoring (lower hematologic toxicity than carbamazepine), but periodic electrolytes are required.
Clinical Pearls
- Oxcarbazepine has a cleaner metabolic profile than carbamazepine (no toxic epoxide metabolite, no autoinduction) but shares its major risk of hyponatremia, which is actually more common with oxcarbazepine.
- As a structural analog of carbamazepine, oxcarbazepine can be used in many of the same indications with a more predictable pharmacokinetic profile.
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Required
Hepatic Adjustment Not required
TDM Required
Concordance Terms
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