Editing Combined oral contraceptive pill (section)

==Drug interactions==
Some [[Medication|drug]]s reduce the effect of the pill and can cause [[breakthrough bleeding]], or increased chance of pregnancy. These include drugs such as [[rifampicin]], [[barbiturate]]s, [[phenytoin]] and [[carbamazepine]]. In addition cautions are given about broad spectrum antibiotics, such as [[ampicillin]] and [[doxycycline]], which may cause problems "by impairing the [[Human flora|bacterial flora]] responsible for recycling [[ethinylestradiol]] from the large bowel" ([[British National Formulary|BNF]] 2003).<!--
 --><ref>The effects of broad-spectrum antibiotics on Combined contraceptive pills is not found on systematic interaction metanalysis (Archer, 2002), although "individual patients do show large decreases in the plasma concentrations of ethinylestradiol when they take certain other antibiotics" (Dickinson, 2001). "experts on this topic still recommend informing oral contraceptive users of the potential for a rare interaction" (DeRossi, 2002) and this remains current (2006) UK [http://www.fpa.org.uk/information/leaflets/documents_and_pdfs/detail.cfm?contentID=130#17 Family Planning Association advice] {{Webarchive|url=https://web.archive.org/web/20070208155326/http://www.fpa.org.uk/information/leaflets/documents_and_pdfs/detail.cfm?contentID=130#17 |date=8 February 2007 }}.</ref><!--
 --><ref>{{cite journal | vauthors = Archer JS, Archer DF | title = Oral contraceptive efficacy and antibiotic interaction: a myth debunked | journal = Journal of the American Academy of Dermatology | volume = 46 | issue = 6 | pages = 917–23 | date = June 2002 | pmid = 12063491 | doi = 10.1067/mjd.2002.120448 }}</ref><!--
 --><ref>{{cite journal | vauthors = Dickinson BD, Altman RD, Nielsen NH, Sterling ML | title = Drug interactions between oral contraceptives and antibiotics | journal = Obstetrics and Gynecology | volume = 98 | issue = 5 Pt 1 | pages = 853–60 | date = November 2001 | pmid = 11704183 | doi = 10.1016/S0029-7844(01)01532-0 | s2cid = 41354899 }}</ref><!--
 --><ref>{{cite journal | vauthors = DeRossi SS, Hersh EV | title = Antibiotics and oral contraceptives | journal = Dental Clinics of North America | volume = 46 | issue = 4 | pages = 653–64 | date = October 2002 | pmid = 12436822 | doi = 10.1016/S0011-8532(02)00017-4 | citeseerx = 10.1.1.620.9933 }}</ref>

The traditional medicinal herb [[St John's Wort]] has also been implicated due to its upregulation of the [[P450]] system in the [[liver]] which could increase the metabolism of ethinyl estradiol and progestin components of some combined oral contraception.<ref>{{cite journal | vauthors = Berry-Bibee EN, Kim MJ, Tepper NK, Riley HE, Curtis KM | title = Co-administration of St. John's wort and hormonal contraceptives: a systematic review | journal = Contraception | volume = 94 | issue = 6 | pages = 668–677 | date = December 2016 | pmid = 27444983 | doi = 10.1016/j.contraception.2016.07.010 | pmc = 11283811 }}</ref>