title: Effect of oral contraceptives on plasma clearance.
abstract: The effects of chronic steroid contraceptive therapy on drug clearance from plasma were studied by using plasma antipyrine, phenylbutazone, and cholecalciferol half-lives in women. After 3 mo of oral steroid therapy (Norinyl, 2 mg; norethindrone + mestranol), the antipyrine half-life was increased in 3 of 6 subjects, phenylbutazone half-life was not consistently altered, and vitamin D3 half-life was increased in 3 of 4 patients. After 1 to 7 yr of oral steroid theraphy, the antipyrine half-life was longer while taking the contraceptive than when the contraceptive treatment was discontinued in 4 of 6 subjects, whereas that of phenylbutazone was not consistently altered.
mesh_terms: D000293:Adolescent; D000328:Adult; D000983:Antipyrine / Q000097:blood*; D002762:Cholecalciferol / Q000097:blood*; D003276:Contraceptives, Oral / Q000494:pharmacology*; D005260:Female; D006207:Half-Life; D006801:Humans; D010653:Phenylbutazone / Q000097:blood*; D011485:Protein Binding / Q000187:drug effects; D013997:Time Factors
chemical_list: D003276:Contraceptives, Oral; D002762:Cholecalciferol; D010653:Phenylbutazone; D000983:Antipyrine