Phenobarbital Contraceptives, hormonal

The most common drugs responsible for acneform eruptions are ACTH, androgenic hormones, anticonvulsants (hydantoin derivatives, phenobarbital, trimethadione), corticosteroids, danazol, disulfiram, halogens (bromides, chlorides, iodides), lithium, oral contraceptives, tuberculostatics (ethionamide, isoniazid, rifampin), vitamins B2, B6, and B12. 

Women receiving anticonvulsants for a seizure disorder require special attention with regard to hormonal contraception. Giving a hormonal contraceptive concomitantly with phenobarbital, carba-mazepine, or phenytoin reduces the contraceptive s efficacy, and many anticonvulsants (e.g., phenytoin) are known teratogens. The use of condoms in conjunction with high-estrogen OCs, injectable progestin-only contraceptives, or intrauterine devices may be considered for these women. ... 

Hormonal contraceptives are less reliable during the use of phenytoin and barbiturates such as phenobarbital and primidone. Intermenstrual breakthrough bleeding and spotting can take place, and pregnancies have occurred. Controlled studies have shown that phenytoin and phenobarbital can reduce contraceptive steroid levels. 

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