The clinical differences between oxcarbazepine (OXC) and carbamazepine (CBZ) are reviewed in terms of efficacy, tolerability, and interaction with other drugs in a study at Universitat Bonn, Berlin, Germany. OXC (Trileptal) is used as monotherapy or adjunctive therapy for the treatment of partial seizures with or without secondary generalization in adults and children above 4 years (USA) or 6 years (Europe) of age. The mechanism of action of OXC resembles CBZ in involving sodium channel blockade; it differs in the type of calcium channel modulation. OXC metabolizes by reduction to the monohydroxy derivative (MHD) and is excreted in the urine after conjugation as a glucuronide, with no autoinduction. CBZ is oxidized to 10, 11-epoxide and is hydrolyzed in the liver. Hepatic metabolism of OXC and enzyme induction are minimal, so that drug combinations show little interaction. OXC is better tolerated and its risk-benefits are superior to CBZ. It causes fewer skin rashes than CBZ; rashes occurred in 3% of patients taking OXC compared to 7% of those treated with CBZ. Cross-reactions may occur, and in patients with known hypersensitivity to CBZ, therapy with OXC should be avoided. The efficacy of oral contraceptives may be impaired by OXC, and risks of teratogenicity remain to be determined. Hyponatremia (<135mEq/L) has occurred more frequently with OXC (30/104 patients, 29%) than with CBZ (69/479 patients, 14.4%). Clinically significant hyponatremia (<125mmol/L) occurred in 2.7% of adults with previously normal values; it is less common in children (0.2%). [1]

COMMENT. The authors recommend OXC as preferable to CBZ because of proven efficacy and lower incidence of side effects. In a multicenter, randomized, double-blind, parallel group trial of 62 newly diagnosed children ages 5 to 17, OXC (Trileptal) in a mean dose of 20 mg/kg/day (range, 8-39 mg/kg/day) provided a >75% reduction in partial seizures in 84% patients, and 100% reduction in 60%. (Report of responses from neurologists provided by Bergman S, Novartis). As add-on therapy in 267 children with partial seizures, a >75% reduction in seizure frequency occurred in 27% vs 7% in patients receiving placebo. Sixty-one percent of neurologists were already using Trileptal as monotherapy for partial seizures in children ages 4-16, and 68% use it as adjunctive therapy. In a review of monotherapy in epilepsy and the role of newer antiepileptic drugs, OXC is as effective as conventional AEDs at controlling partial seizures and is better tolerated. [2]

Oxcarbazepine exacerbates myoclonic and absence seizures in juvenile idiopathic generalized epilepsies (IGE), in a report from Montpellier and Marseille, France [3]. Six patients, ages 6 to 19 years, with juvenile IGE were affected; 5 had worsening of myoclonic jerks, 3 had exacerbation of absence seizures (one had absence status); and 3 had a slight increase in generalized tonic clonic seizures.