Interaction entre Éfavirenz et Tiagabine

Use of tiagabine HCl without enzyme-inducing antiepileptic drugs results in blood levels about twice those attained in the studies on which current dosing recommendations are based (see DOSAGE AND ADMINISTRATION ).

Tiagabine HCl is considered to be a non-enzyme inducing AED (see PRECAUTIONS, General, Use in Non-Induced Patients ).

…tiagabine HCl dosing recommendations in current labeling for treatment of epilepsy were based on use in patients with partial seizures 12 years of age and older, most of whom were taking enzyme-inducing antiepileptic drugs (AEDs; e.g., carbamazepine, phenytoin, primidone and phenobarbital) which lower plasma levels of tiagabine HCl by inducing its metabolism.

Carbamazepine, phenytoin, primidone, and phenobarbital are generally classified as enzyme inducers; valproate and gabapentin are not.

Effects of other Antiepilepsy Drugs (AEDs) on Tiagabine HCl: Carbamazepine : Population pharmacokinetic analyses indicate that tiagabine clearance is 60% greater in patients taking carbamazepine with or without other enzyme-inducing AEDs.

Patients who are receiving concomitant anticonvulsant medications primarily metabolized by the liver, such as phenytoin and phenobarbital, may require periodic monitoring of plasma levels [see Drug Interactions ( 7.1 ) ] .

Anticonvulsants:Carbamazepine PhenytoinPhenobarbital ↓ carbamazepine * ↓ efavirenz * ↓ anticonvulsant ↓ efavirenz There are insufficient data to make a dose recommendation for efavirenz.

Potential for reduction in anticonvulsant and/or efavirenz plasma levels; periodic monitoring of anticonvulsant plasma levels should be conducted.

Alternative anticonvulsant treatment should be used.