Decreased efficacy Drugs or herbal products that induce certain enzymes, including CYP3A4, may decrease the effectiveness of COCs or increase breakthrough bleeding. Some drugs or herbal products that may decrease the effectiveness of hormonal contraceptives include phenytoin, barbiturates, carbamazepine, bosentan, felbamate, griseofulvin, oxcarbazepine, rifampicin, topiramate and products containing St. John’s wort. Interactions between oral contraceptives and other drugs may lead to breakthrough bleeding and/or contraceptive failure.” “Use an alternative method of contraception or a back-up method when enzyme inducers are used with COCs, and to continue back-up contraception for 28 days after discontinuing the enzyme inducer to ensure contraceptive reliability.CYP3A4 inhibitors such as itraconazole or ketoconazole may increase plasma hormone levels.” Antivirals ‘Significant changes (increase or decrease) in the plasma levels of estrogen and progestin have been noted in some cases of co-administration with HIV protease inhibitors or with non-nucleoside reverse transcriptase inhibitors.” Antibiotics “There have been reports of pregnancy while taking hormonal contraceptives and antibiotics, but clinical pharmacokinetic studies have not shown consistent effects of antibiotics on plasma concentrations of synthetic steroids.” Others “COCs containing EE may inhibit the metabolism of other compounds. COCs have been shown to significantly decrease plasma concentrations of lamotrigine. This may reduce seizure control; therefore, dosage adjustments of lamotrigine may be necessary.”
Drospirenone/ethinylestradiol/levomefolic acid
Ethinylestradiol/drospirenone
Estradiol enantate/algestone acetophenide
Ethinylestradiol/norethisterone
Ethinylestradiol sulfonate/norethisterone acetate
Ethinylestradiol/cyproterone acetate
Conjugated estrogens/norgestrel
Ethinylestradiol/megestrol acetate