Oxcarbazepine (Adverse effects)

Individuals carrying variants such as HLA-B*15:02 may develop serious skin reactions during treatment with oxcarbazepine.

Oxcarbazepine is an antiepileptic drug used for the treatment of focal seizures in adults and children. It is a keto derivative of carbamazepine developed to maintain its therapeutic efficacy with a more favorable drug interaction profile.

Although generally well-tolerated, oxcarbazepine can be associated with cutaneous adverse reactions ranging from mild rashes to severe hypersensitivity syndromes. The identification of pharmacogenetic factors has made it possible to characterize patients at higher risk of developing these reactions. Among them, the HLA-B*15:02 allele is the main pharmacogenetic marker associated with the risk of developing severe cutaneous adverse reactions induced by oxcarbazepine.

Mechanism of action

Oxcarbazepine exerts its therapeutic effect primarily by selectively blocking voltage-dependent sodium channels present in neurons. This mechanism stabilizes hyperexcitable neuronal membranes, reduces the propagation of repetitive electrical discharges, and decreases the transmission of abnormal nerve impulses.

Oxcarbazepine is a prodrug whose active metabolite, 10-monohydroxy derivative (MHD), is responsible for most of the drug's anticonvulsant activity. It can be used both as monotherapy and in combination with other antiepileptic drugs.

Contraindications

Oxcarbazepine is contraindicated in patients with known hypersensitivity to the active substance or any of its excipients. It should be used with caution in patients with a history of hypersensitivity to carbamazepine, due to possible cross-reactivity between both drugs.

Likewise, in patients carrying the HLA-B*15:02 allele, especially those who have not previously received oxcarbazepine, the use of alternative treatments should be considered due to the increased risk of developing Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN).

Adverse reactions

Most of the adverse effects associated with oxcarbazepine are mild to moderate and include dizziness, somnolence, headache, fatigue, nausea, vomiting, diplopia, blurred vision, and coordination disturbances.

Hyponatremia may also occur, especially during prolonged treatment or in elderly patients.

Rarely, severe cutaneous adverse reactions (SCAR) may develop, including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and drug reaction with eosinophilia and systemic symptoms (DRESS).

Brand names

• Trileptal®
• Oxtellar XR®