oxcarbazepine: clinical use

Prescribing considerations

• Review previous carbamazepine hypersensitivity; cross-reactivity occurs in a substantial minority.
• Consider HLA-B*1502 testing in genetically at-risk Asian populations before treatment; testing does not replace clinical vigilance.
• Assess renal function, hepatic disease, baseline sodium risk, cardiac conduction disease and interacting medicines.
• Oxcarbazepine may reduce hormonal contraceptive effectiveness and should not be withdrawn abruptly.

Contraindications and cautions

• Hypersensitivity to oxcarbazepine, eslicarbazepine or a formulation excipient.
• Do not restart after withdrawal for an oxcarbazepine hypersensitivity reaction.

Monitoring

• Check serum sodium according to clinical risk, particularly with renal disease, heart failure, older age or sodium-lowering medicines, and if compatible symptoms occur.
• Monitor thyroid function in children.
• Evaluate liver function or blood counts when clinical features suggest hepatic or haematological toxicity.
• Routine plasma-level monitoring is not usually informative, but MHD measurement may help with altered renal function, pregnancy, suspected non-adherence or enzyme-inducing combinations.

Clinical pharmacology

Oxcarbazepine is extensively reduced to the active monohydroxy derivative MHD. MHD primarily blocks voltage-sensitive sodium channels; it is eliminated largely through renal metabolism and excretion. Oxcarbazepine and MHD induce CYP3A4/3A5 and inhibit CYP2C19, creating clinically relevant interactions.

Formulation and product differences

• The selected film-coated tablet contains lactose; its score line is for easier swallowing, not equal dose division.
• The oral suspension requires vigorous shaking and measurement with the supplied syringe. It contains sorbitol, propylene glycol, parabens and a small amount of ethanol.
• The opened oral-suspension bottle should be discarded after the product-specific in-use period stated in its leaflet.

Oral suspension

Route: Oral

Strengths: 60 mg/mL

Tablet

Route: Oral

Strengths: 150 mg, 300 mg, 600 mg