Charcoal treatment and risk of escape ovulation in oral contraceptive users

Ovulatory potential was studied during the use of two oral contraceptive pill preparations after repeated mid-cycle administration of activated charcoal. Eleven women used monophasic pills containing gestodene 75 µg plus ethinyl oestradiol 30 µg or norethisterone acetate 1 mg plus ethinyl oestradiol 30 µg for 4 months each in randomized order. During both pill treatments the third cycle was a control cycle and during the fourth cycle of both pill types 5 g of activated charcoal was ingested four times a day starting 3 h after pill intake on cycle days 12 13 and 14. Ovarian activity was monitored by intravaginal ultrasonography of follicles and by measurements of serum concentrations of LH FSH oestradiol and progesterone throughout the control and charcoal-treatment cycles of both pill treatments. None of the women ovulated. Follicular activity seen in two women did not correlate with charcoal administration. It is concluded that the possible enterohepatic recirculation of gestodene and norethisterone is not of clinical importance. Repeated charcoal treatment when administered 3 h after but at least 12 h before pill intake can be used to treat diarrhoea in women taking oral contraceptives. (authors)