Oral contraceptives hormonal antiepileptics

Co-cyprindiol is a mixture of the anti-androgenic progestogen, cyproter-one acetate 2 mg, with ethinylestradiol 35 micrograms. It is used for the treatment of acne and moderately severe hirsutism in women who may also wish to use it as an oral contraceptive, and its contraceptive efficacy is expected to be reduced by the same hepatic enzyme inducers (see Table 28. r, (p.975)) that interact with conventional combined oral contraceptives. The precautions described in this section for the combined hormonal contraceptives with the various drugs listed in Table 28.1 , (p.975), should therefore be followed, see Hormonal contraceptives + Antiepileptics Barbiturates or Phenytoin , p.985. 

Preliminary results of a study show that rufinamide 800 mg twice daily for 14 days decreased the AUC of ethinylestradiol 35 micrograms hy 22% and of norethisterone 1 mg by 14% in healthy women taking a combined oral contraceptive. Inhibition of ovulation was not assessed. These reductions in plasma levels of the contraceptive hormones are similar to those seen with topiramate (see Hormonal contraceptives + Antiepileptics Topiramate , below), and their clinical relevance is unknown. However, given these findings, low-dose contraceptives (ethinylestradiol 20 micrograms) may be considered unsuitable for use with rufinamide. Further study is needed. 

It is likely that nevirapine induces the metabolism of the components of the oral contraceptive by cytochrome P450 isoenzymes. Although it is not known whether these modest reductions in levels would reduce the anti-ovulatory efficacy of the combined oral contraceptive, it would be prudent to assume they could. The manufacturers recommend that combined oral contraceptives and other hormonal methods of birth control should not be used as the sole method of contraception in women taking nevirapine. They suggest that a barrier method (e.g. condoms) should also be used, and note that this is also advisable to reduce the risk of HTV transmission. The Faculty of Family Planning and Reproductive Health Care (FFPRHC) Clinical Effectiveness Unit notes that nevirapine can induce liver enzymes and may reduce the levels of ethinylestradiol and progestogens. They therefore recommend that their guidance on hormonal contraceptives and liver enzyme inducers is followed, see Hormonal contraceptives + Antiepileptics Barbiturates or Phenytoin , p.985 for fiir-ther detail. 

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