Examination of the potential interaction between ketoconazole (Nizoral) and oral contraceptives with special regard to products of low hormone content (Rigevidon, anteovin).

Abstract

The possibility of drug interaction between oral contraceptives and the antibiotic ketoconazole (Nizoral) was explored by treating oral contraceptive users who needed treatment for vaginal candidiasis during pill intake rather than during the pill-free days of the cycle. 47 women taking Ovidon (0.25 mg d-norgestrel and 0.05 mg ethinyl estradiol combined) 39 women taking Rigevidon (0.15 mg d-norgestrel and 0.03 mg ethinyl estradiol combined) and 61 women taking Anteovin (0.05 and 0.125 mg d-norgestrel and 0.05 mg ethinyl estradiol sequential) were treated with 400 mg Nizoral daily for 5 days. None of the women had previously reported breakthrough bleeding nor were any o f them harboring trichomonas. There were 6 incidents of spotting and 1 of breakthrough bleeding but no pregnancies. Bleeding fell on Days 2-5 of Nizoral. Bleeding always occurred in the secretory phase or during the 1st 11 days of the sequential when hormone doses were lower. 32 women were treated a 2nd time with Nizoral and 2 of these had spotting 1 with Rigevidon and 1 with Anteovin. It appears that ketoconazole decreases the effect of contraceptives.