Oxcarbazepine extended-release

Phenytoin, Carbamazepine, and Phenobarbital: Coadministration decreased blood levels of an active metabolite of oxcarbazepine extended-release tablets: Greater dosage of oxcarbazepine extended-release tablets may be required. ( 2.5 , 7.2 ) Oral Contraceptives: Advise patients that oxcarbazepine extended-release tablets may decrease the effectiveness of hormonal contraceptives. Additional non-hormonal forms of contraception are recommended. ( 7.3 )

7.1 Effect of Oxcarbazepine Extended-Release Tablets on Other Drugs It is recommended that the plasma levels of phenytoin be monitored during the period of oxcarbazepine extended-release tablets titration and dosage modification [see Clinical Pharmacology ( 12.3 )]. A decrease in the dosage of phenytoin may be required.

7.2 Effect of Other Drugs on Oxcarbazepine Extended-Release Tablets If oxcarbazepine extended-release tablets and strong CYP3A4 inducers or UGT inducers (e.g., rifampin, carbamazepine, phenytoin and phenobarbital) are administered concurrently, it is recommended that the plasma levels of MHD be monitored during the period of oxcarbazepine extended-release tablets titration [see Clinical Pharmacology ( 12.3 )]. Dosage adjustment of oxcarbazepine extended-release tablets may be required after initiation, dosage modification, or discontinuation of such inducers [see Dosage and Administration ( 2.5 )].

7.3 Hormonal Contraceptives Concurrent use of immediate-release oxcarbazepine with hormonal contraceptives may render these contraceptives less effective [see Clinical Pharmacology ( 12.3 )]. Studies with other oral or implant contraceptives have not been conducted.

8.1 Pregnancy Risk Summary There are no adequate data on the developmental risks associated with the use of oxcarbazepine extended-release tablets in pregnant women; however, oxcarbazepine extended-release tablets is closely related structurally to carbamazepine, which is considered to be teratogenic in humans. Data on a limited number of pregnancies from pregnancy registries suggest that oxcarbazepine monotherapy use is associated with congenital malformations (e.g., craniofacial defects such as oral clefts, and cardiac malformations such as ventricular septal defects).

Increased incidences of fetal structural abnormalities and other manifestations of developmental toxicity (embryolethality, growth retardation) were observed in the offspring of animals treated with either oxcarbazepine or its active 10-hydroxy metabolite (MHD) during pregnancy at doses similar to the maximum recommended human dose (MRHD). In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. The background risk of major birth defects and miscarriage for the indicated population is unknown.

Clinical Considerations An increase in seizure frequency may occur during pregnancy because of altered levels of the active metabolite of oxcarbazepine. Monitor patients carefully during pregnancy and through the postpartum period [see Warnings and Precautions ( 5.9 )] Data Human Data Data from published registries have reported craniofacial defects such as oral clefts and cardiac malformations such as ventricular septal defects in children with prenatal oxcarbazepine exposure.

Animal Data When pregnant rats were given oxcarbazepine (30 mg/kg/day, 300 mg/kg/day, or 1,000 mg/kg/day) orally throughout the period of organogenesis, increased incidences of fetal malformations (craniofacial, cardiovascular, and skeletal) and variations were observed at the intermediate and high doses (approximately 1.2 and 4 times, respectively, the MRHD on a mg/m 2 basis). Increased embryofetal death and decreased fetal body weights were seen at the high dose. Doses ≥ 300 mg/kg were also maternally toxic (decreased body weight gain, clinical signs), but there is no evidence to suggest that teratogenicity was secondary to the maternal effects.

In a study in which pregnant rabbits were orally administered MHD (20 mg/kg/day, 100 mg/kg/day, or 200 mg/kg/day) during organogenesis, embryofetal mortality was increased at the highest dose (1.5 times the MRHD on a mg/m 2 basis). This dose produced only…

8.3 Females and Males of Reproductive Potential Contraception Use of oxcarbazepine extended-release tablets with hormonal contraceptives containing ethinylestradiol or levonorgestrel is associated with decreased plasma concentrations of these hormones and may result in a failure of the therapeutic effect of the oral contraceptive drug. Advise women of reproductive potential taking oxcarbazepine extended-release tablets who are using a contraceptive containing ethinylestradiol or levonorgestrel to use additional or alternative non-hormonal birth control [see Drug Interactions ( 7.3 ) and Clinical Pharmacology ( 12.3 )] .