title: Inhibition of hepatic drug metabolism by norethindrone.
abstract: In order to assess the effect of norethindrone on hepatic drug metabolism in man, hepatic N-demethylation of aminopyrine was studied by means of the aminopyrine breath test (ABT) in 7 healthy women during two menstrual cycles. Aminopyrine metabolic clearance rates were also studied in 3 women. The women were examined at the ends of the first, second, and third weeks before starting progestogen therapy and at the same times during a second menstrual cycle during which they took norethindrone, 350 microgram/day. The ABT was 5.1 +/- 1.9% (mean +/- SD) during the three control weeks and lower (p less than 0.001) during the three weeks on norethindrone, 3.9 +/- 0.9%. Aminopyrine metabolic clearance rate also fell during norethindrone therapy. The data suggest that progestogens inhibit hepatic microsomal function.
mesh_terms: D000328:Adult; D000632:Aminopyrine / Q000378:metabolism; D001944:Breath Tests; D005260:Female; D006801:Humans; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008657:Metabolic Clearance Rate / Q000187:drug effects; D009640:Norethindrone / Q000494:pharmacology*; D004364:Pharmaceutical Preparations / Q000378:metabolism*
chemical_list: D004364:Pharmaceutical Preparations; D000632:Aminopyrine; D009640:Norethindrone