Felbamate

Felbamate decreases steady-state carbamazepine plasma concentrations by 31% while increasing carbamazepine epoxide concentrations by 57%, potentially reducing carbamazepine efficacy.

Enzyme inhibitor that decreases valproate clearance. Increased monitoring of valproate concentrations and dosage adjustment indicated.

Increases metabolism of contraceptive steroids, reducing contraceptive effectiveness and potentially resulting in unintended pregnancy or unscheduled bleeding.

May reduce contraceptive effectiveness and result in unintended pregnancy or breakthrough bleeding by increasing metabolism of contraceptive steroids.

May decrease contraceptive effectiveness and increase breakthrough bleeding through CYP3A4 induction.

May decrease plasma concentrations of COCs and potentially diminish effectiveness or increase breakthrough bleeding.

Felbamate increases steady-state phenytoin plasma concentrations, requiring approximately 20-40% dose reduction of phenytoin to maintain therapeutic levels and avoid adverse effects.

Felbamate increases steady-state valproate plasma concentrations in a dose-dependent manner, requiring monitoring and possible valproate dose adjustment.

Induces CYP3A4 and may decrease plasma concentrations of desogestrel and ethinyl estradiol, potentially diminishing contraceptive effectiveness and increasing breakthrough bleeding.

May decrease systemic concentrations of hormonal contraceptives and diminish effectiveness or increase breakthrough bleeding.

Induces CYP3A4 enzyme, may decrease effectiveness of COCs or increase breakthrough bleeding.

May decrease the effectiveness of hormonal contraceptives or increase breakthrough bleeding through CYP3A4 enzyme induction.

Enzyme inducer that may decrease effectiveness of COCs or increase breakthrough bleeding. Use back-up contraception.

CYP3A4 enzyme inducer that may decrease the effectiveness of the contraceptive or increase breakthrough bleeding.

May decrease plasma concentrations of etonogestrel and diminish contraceptive effectiveness or increase breakthrough bleeding.

CYP3A4 enzyme inducer that may decrease plasma concentrations of etonogestrel and ethinyl estradiol, potentially diminishing contraceptive effectiveness or increasing breakthrough bleeding.

Induces CYP3A4, may decrease plasma concentrations of CHCs and potentially diminish effectiveness or increase breakthrough bleeding.

May increase phenytoin serum levels; monitoring of phenytoin levels recommended.

Felbamate induces CYP3A4 and may decrease plasma concentrations of COCs, potentially diminishing contraceptive effectiveness or increasing breakthrough bleeding.

Felbamate induces CYP3A4 enzymes, potentially decreasing contraceptive effectiveness and increasing breakthrough bleeding.

May decrease effectiveness of medroxyprogesterone acetate through enzyme induction. Counsel use of back-up or alternative contraception.

Enzyme inducer that may decrease plasma concentrations of CHCs and potentially diminish effectiveness or increase breakthrough bleeding.

CYP3A4 inducer that may decrease the effectiveness of COCs or increase breakthrough bleeding.

Enzyme inducer that may decrease plasma concentrations of norethindrone and ethinyl estradiol, potentially diminishing contraceptive effectiveness or increasing breakthrough bleeding.

May decrease plasma concentrations and efficacy of contraceptive; may increase breakthrough bleeding.

Felbamate increases steady-state phenobarbital plasma concentrations while decreasing felbamate concentrations; phenobarbital dosing adjustment may be necessary.

May increase phenytoin serum levels; monitoring of phenytoin levels recommended.

Metabolic enzyme inducer that may decrease systemic concentrations of estrogen and/or progestin, potentially diminishing contraceptive effectiveness.

CYP3A4 inducer decreases plasma concentrations of ulipristal acetate and may decrease its effectiveness as emergency contraception.

Felbamate is an enzyme inhibitor that can decrease valproate clearance. Monitoring of valproate and felbamate concentrations and dosage adjustment are indicated.

Enzyme inhibitor that can decrease valproate clearance. Increased monitoring of valproate and concomitant drug concentrations and dosage adjustment indicated.

Suspected of causing SIADH; may increase pressor and antidiuretic effects of vasopressin. Hemodynamic monitoring recommended.

May cause SIADH, increasing pressor and antidiuretic effects of vasopressin. Hemodynamic monitoring recommended; adjust vasopressin dose as needed.

CYP2C19 inhibitor and CYP3A4 inducer that does not affect clonazepam pharmacokinetics.

Effects of Erythromycin on Felbamate The coadministration of erythromycin (1000 mg/day) for 10 days did not alter the pharmacokinetic parameters of C max , C min , AUC, Cl/kg or T max at felbamate daily doses of 3000 or 3600 mg/day in 10 otherwise healthy subjects with epilepsy.