If taken together with drugs that induce the CYP3A4 cytochrome P450 liver enzyme,<unk>  may be metabolized faster and may have lower effectiveness. These include, but are not limited to barbiturates, bosentan, carbamazepine, felbamate, griseofulvin, oxcarbazepine, phenytoin, rifampin, St. John's wort and topiramate.
Levonorgestrel
Etonogestrel
Norgestrel
Desogestrel
Chloroethynylnorgestrel
Gestodene
5α-Dihydrolevonorgestrel
Norelgestromin