[Pill cycle disturbance in simultaneous use of itraconazole and oral contraceptives]

Since the introduction of itraconazole in the Netherlands, the Netherlands Pharmacovigilance Foundation LAREB and the Inspectorate for Health Care received 15 reports of pill cycle disturbances and one of pregnancy occurring during simultaneous use of itraconazole and oral contraceptives. Twelve women used oral contraceptives containing ethinylestradiol and desogestrel. In these women, the withdrawal bleeding was either delayed or did not occur at all; one of these women reported a transiently positive pregnancy test after previous breakthrough bleedings. Three women who used a contraceptive containing ethinylestradiol and levonorgestrel had a breakthrough bleeding. One woman who used an oral contraceptive containing ethinylestradiol and cyproterone acetate became pregnant during the concomitant use of itraconazole. The possible mechanism involved remains to be explained. Although an influence of itraconazole on the reliability of oral contraceptives is uncertain, additional contraceptive measurements might be considered.