Trileptal (Oxcarbazepine) - Drug Interactions, Contraindications, Overdosage, etc

DRUG INTERACTIONS

Antiepileptic Drugs

Potential interactions between Trileptal and other AEDs were assessed in clinical studies. The effect of these interactions on mean AUCs and C_min are summarized in Table3.

Table3: Summary of AED Interactions with Trileptal^®

AED Coadministered	Dose of AED (mg/day)	Trileptal Dose (mg/day)	Influence of Trileptal on AED Concentration (Mean Change, 90% Confidence Interval)	Influence of AED on MHD Concentration (Mean Change, 90% Confidence Interval)
Carbamazepine	400-2000	900	nc1	40% decrease [CI: 17% decrease, 57% decrease]
Phenobarbital	100-150	600-1800	14% increase [CI: 2% increase, 24% increase]	25% decrease [CI: 12% decrease, 51% decrease]
Phenytoin	250-500	600-1800 >1200-2400	nc1,2 up to 40% increase3  [CI: 12% increase, 60% increase]	30% decrease [CI: 3% decrease, 48% decrease]
Valproic acid	400-2800	600-1800	nc1	18% decrease [CI: 13% decrease, 40% decrease]

¹ nc denotes a mean change of less than 10%

² Pediatrics

³ Mean increase in adults at high Trileptal doses

In vivo, the plasma levels of phenytoin increased by up to 40% when Trileptal was given at doses above 1200 mg/day. Therefore, when using doses of Trileptal greater than 1200 mg/day during adjunctive therapy, a decrease in the dose of phenytoin may be required. The increase of phenobarbital level, however, is small (15%) when given with Trileptal.

Strong inducers of cytochrome P450 enzymes (i.e., carbamazepine, phenytoin and phenobarbital) have been shown to decrease the plasma levels of MHD (29%-40%).

No autoinduction has been observed with Trileptal.

Hormonal Contraceptives

Coadministration of Trileptal with an oral contraceptive has been shown to influence the plasma concentrations of the two hormonal components, ethinylestradiol (EE) and levonorgestrel (LNG). The mean AUC values of EE were decreased by 48% [90% CI: 22-65] in one study and 52% [90% CI: 38-52] in another study. The mean AUC values of LNG were decreased by 32% [90% CI: 20-45] in one study and 52% [90% CI: 42-52] in another study. Therefore, concurrent use of Trileptal with hormonal contraceptives may render these contraceptives less effective (see Drug Interactions subsection). Studies with other oral or implant contraceptives have not been conducted.

Calcium Antagonists

After repeated coadministration of Trileptal, the AUC of felodipine was lowered by 28% [90% CI: 20-33].

Verapamil produced a decrease of 20% [90% CI: 18-27] of the plasma levels of MHD.

Other Drug Interactions

Cimetidine, erythromycin and dextropropoxyphene had no effect on the pharmacokinetics of MHD. Results with warfarin show no evidence of interaction with either single or repeated doses of Trileptal.

Drug/Laboratory Test Interactions

There are no known interactions of Trileptal with commonly used laboratory tests.

OVERDOSAGE

Human Overdose Experience

Isolated cases of overdose with Trileptal^® (oxcarbazepine) have been reported. The maximum dose taken was approximately 24,000 mg. All patients recovered with symptomatic treatment.

Treatment and Management

There is no specific antidote. Symptomatic and supportive treatment should be administered as appropriate. Removal of the drug by gastric lavage and/or inactivation by administering activated charcoal should be considered.

CONTRAINDICATIONS

Trileptal^® (oxcarbazepine) should not be used in patients with a known hypersensitivity to oxcarbazepine or to any of its components.

DRUG ABUSE AND DEPENDENCE

Abuse

The abuse potential of Trileptal^® (oxcarbazepine) has not been evaluated in human studies.

Dependence

Intragastric injections of oxcarbazepine to four cynomolgus monkeys demonstrated no signs of physical dependence as measured by the desire to self-administer oxcarbazepine by lever pressing activity.