Which medications are known to reduce the effectiveness of the Combined Oral Contraceptive Pill (COCP)?

The Combined Oral Contraceptive Pill (COCP) can have its effectiveness reduced by certain medications that induce liver enzymes or alter hormone metabolism. Rifamycins, carbamazepine, and griseofulvin are all known to have such interactions.

Rifamycins, including rifampicin and rifabutin, are potent enzyme inducers that can increase the metabolism of estrogen and progestin components of the COCP, potentially leading to decreased contraceptive efficacy. This is particularly relevant in the context of treating tuberculosis or other infections where rifamycins are prescribed.

Carbamazepine, primarily used as an anticonvulsant and mood-stabilizing drug, also acts as a liver enzyme inducer. This means it can accelerate the breakdown of contraceptive hormones, thereby reducing their effectiveness and increasing the risk of unintended pregnancy.

Griseofulvin, an antifungal medication primarily used to treat dermatophyte infections, similarly induces hepatic enzymes, resulting in altered metabolism of the hormones in the COCP.

In contrast, the other options contain medications that do not exhibit significant enzyme-inducing properties related to hormonal contraceptives. For instance, lisinopril is an antihypertensive that does not interfere with