The effects of ampicillin oral contraceptive steroids in women.

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Abstract
1 Thirteen women taking long term oral contraceptive steroids were studied while taking ampicillin (500 mg three times daily) and compared to a control cycle while not taking ampicillin. 2 There were no significant changes in the plasma concentrations of ethinyloestradiol, levonorgestrel, follicle stimulating hormone or progesterone, although lower concentrations of ethinyloestradiol were noted in two women. 3 We conclude that most patients taking oral contraceptive steroids do not need to take alternative contraceptive precautions while taking ampicillin.