title: Impact of combined oral contraceptives containing ethinylestradiol on the liver microsomal metabolism.
abstract: OBJECTIVE
  To check whether currently used combined oral contraceptives (COCs) containing ethinylestradiol (EE) affect the liver microsomal metabolism.
  
  
  METHODS
  (13)C-methacetin breath test ((13)C-MBT) - a sensitive non-invasive probe of cytochrome P-450 1A2 activity - was performed in 15 women on day 14, 15, 16, 17 or 18 of intake of their COC (containing EE), and between day 1 and 5 during the withdrawal bleeding, as well as in nine women not using hormonal contraception during the luteal phase of their cycle (between the 17th and the 23rd day), and between day 1 and 5 during menstruation.
  
  
  RESULTS
  The maximum breath (13)C elimination was significantly lower during the phase of intake of contraceptive pills than during withdrawal bleeding: 31.5 ± 2.2 %/h vs. 38.2 ± 1.9 %/h (p = 0.0045), whereas the time to reach it was similar on the two study days: 21.2 ± 1.2 min vs. 21.0 ± 1.1 min. Between the 27th and the 180th min of observation the cumulative breath (13)C elimination was statistically significantly lower during intake of the pill than during withdrawal bleeding. No significant menstrual cycle phase-dependent fluctuations in the results of the (13)C- methacetin breath test were observed in the control group.
  
  
  CONCLUSIONS
  COCs containing EE markedly inhibit hepatic microsomal function. This phenomenon must be taken into consideration when interpreting results of (13)C-MBT.
authors: Department of Basic Biomedical Science, School of Pharmacy, Medical University of Silesia, Sosnowiec, Poland. kjonderko@sum.edu.pl
authors: Krzysztof
authors: K
authors: Jonderko
authors: Piotr
authors: P
authors: Skałba
authors: Anna
authors: A
authors: Kasicka-Jonderko
authors: Magdalena
authors: M
authors: Kamińska
authors: Dorota
authors: D
authors: Bizior-Frymus
authors: Renata
authors: R
authors: Dyja
mesh_terms: D000081:Acetamides; D000328:Adult; D000736:Androstenes / Q000494:pharmacology; D001944:Breath Tests; D002250:Carbon Radioisotopes; D016022:Case-Control Studies; D003277:Contraceptives, Oral, Combined / Q000494:pharmacology*; D017373:Cyproterone Acetate / Q000494:pharmacology; D019388:Cytochrome P-450 CYP1A2 / Q000187:drug effects* / Q000378:metabolism; D017135:Desogestrel / Q000494:pharmacology; D004338:Drug Combinations; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000494:pharmacology; D008099:Liver / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008597:Menstrual Cycle / Q000502:physiology; D009644:Norgestrel / Q000031:analogs & derivatives / Q000494:pharmacology; D009652:Norpregnenes / Q000494:pharmacology; D055815:Young Adult
chemical_list: D000081:Acetamides; D000736:Androstenes; D002250:Carbon Radioisotopes; D003277:Contraceptives, Oral, Combined; D004338:Drug Combinations; D009652:Norpregnenes; C534342:drospirenone and ethinyl estradiol combination; C072593:ethinyl estradiol, levonorgestrel drug combination; C442659:ethinyl estradiol-desogestrel combination; C109079:norgestimate, ethinyl estradiol drug combination; C035495:methacetin; C033273:Gestodene; D009644:Norgestrel; D004997:Ethinyl Estradiol; D017373:Cyproterone Acetate; D016912:Levonorgestrel; C032640:Cyproterone acetate, ethinyl estradiol drug combination; D017135:Desogestrel; C504573:CYP1A2 protein, human; D019388:Cytochrome P-450 CYP1A2