Metabolism of Oral Contraceptives II. Metabolism of Norethynodrel in Women

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Abstract
1. The metabolism of norethynodrel was investigated in four women. In seven days following oral administration, 40% of the dose was excreted in the urine and 34% in the faeces, predominantly in conjugated form. The urinary half-life was 11 h. 2. Fractionation of the urinary metabolites revealed a complex and extensive metabolic pattern. The metabolites isolated and identified from the less polar fractions were: 17α-ethynylestr-5(10)-ene-3α,17β-diol (1.8% total urinary radioactivity); 17α-ethynylestr-5(10)-ene-3β,17β-diol (4.7%); 17α-ethynyl-5β-estrane-3α,17β-diol (1.0%); and 17α-ethynyl-5α-estrane-3β,17β-diol (2.3%), unchanged norethynodrel was not isolated.