There was no observable tolerance during a four weeks course of treatment with daily administration of oxcarbazepine or licarbazepine in electroshock test on mice and rats. Most of the antiepileptic activity can be attributed to licarbazepine. Aside from its reduction in side effects, it is presumed to have the same main mechanism as carbamazepine, sodium channel inhibition, and is generally used to treat the same conditions. Pharmacogenetics
The human leukocyte antigen (HLA) allele B*1502 has been associated with an increased incidence of Stevens–Johnson syndrome and toxic epidermal necrolysis in people treated with carbamazepine, and thus those treated with oxcarbazepine might have similar risks. People of Asian descent are more likely to carry this genetic variant, especially some Malaysian populations, Koreans (2%), Han Chinese (2–12%), Indians (6%), Thai (8%), and Philippines (15%). Therefore, it has been suggested to consider genetic testing in these people prior to initiation of treatment. Structure
Oxcarbazepine is a structural derivative of carbamazepine, with a ketone in place of the carbon–carbon double bond on the dibenzazepine ring at the 10 position (10-keto). This difference helps reduce the impact on the liver of metabolizing the drug, and also prevents the serious forms of anemia or agranulocytosis occasionally associated with carbamazepine. Aside from this reduction in side effects, it is thought to have the same mechanism as carbamazepine — sodium channel inhibition (presumed to be the main mechanism of action) – and is generally used to treat the same conditions. Oxcarbazepine is a prodrug which is activated to licarbazepine in the liver.
There is some evidence to support its effectiveness in reducing seizure frequency when used as an add-on therapy for drug-resistant focal epilepsy but there are concerns over tolerability. Pregnancy
There is limited data analyzing the impact of oxcarbazepine on a human fetus. Animal studies have shown increased fetal abnormalities in pregnant rats and rabbits exposed to oxcarbazepine during pregnancy. In addition, oxcarbazepine is structurally similar to carbamazepine, which is considered to be teratogenic in humans (pregnancy category D). Oxcarbazepine should only be used during pregnancy if the benefits justify the risks.Pregnant women on oxcarbazepine should be closely monitored, as plasma levels of the active metabolite licarbazepine have been shown to potentially decrease during pregnancy. Breastfeeding
Oxcarbazepine and its metabolite licarbazepine are both present in human breast milk and thus, some of the active drug can be transferred to a nursing infant. When considering whether to continue this medication in nursing mothers, the impact of the drugs side effect profile on the infant, should be weighed against its anti-epileptic benefit for the mother. Side effects
Side effects are dose-dependent. The most common include dizziness, blurred or double vision, nystagmus, ataxia, fatigue, headaches, nausea, vomiting, sleepiness, difficulty in concentration and mental sluggishness.Other rare side effects of oxcarbazepine include severe low blood sodium (hyponatremia), anaphylaxis / angioedema, hypersensitivity (especially if experienced with carbamazepine), toxic epidermal necrolysis, Stevens–Johnson syndrome, and thoughts of suicide.Measurement of serum sodium levels should be considered in maintenance treatment or if symptoms of hyponatremia develop.