Birth control pill formulations explained

Birth control pills come in a variety of formulations. The main division is between combined oral contraceptive pills, containing both estrogens and synthetic progestogens (progestins), and progestogen only pills. Combined oral contraceptive pills also come in varying types, including varying doses of estrogen, and whether the dose of estrogen or progestogen changes from week to week.

Mechanism of action

Combination pills usually work by preventing the ovaries from releasing eggs (ovulation). They also thicken the cervical mucus, which keeps sperm from penetrating into the uterus and joining with an egg. The hormones in combination and progestogen-only pills also thin the lining of the uterus. This could prevent pregnancy by interfering with implantation of a blastocyst.

Main action in typical use is prevention of ovulation.

Combined oral contraceptive pills

All contain an estrogen, ethinylestradiol or mestranol,[1] [2] in varying amounts, and one of a number of different progestogens. (Regarding the estrogen, the inactive 3-methyl ether of ethinylestradiol, which must be metabolized by the liver into the active ethinylestradiol; 50 μg of mestranol is equivalent to only 35 μg of ethinylestradiol and should not be used when high-dose [50 μg ethinylestradiol] estrogen pills are needed; mestranol was the estrogen used in the first oral contraceptive, Enovid). They are usually taken for 21 days with then a seven-day gap during which a withdrawal bleed (often, but incorrectly, referred to as a menstrual period) occurs. These differ in the amount of estrogen given, and whether they are monophasic (the same dose of estrogen and progestogen during each of the 21 days) or multiphasic (varying doses). The introduction of extended-cycle monophasic pills (i.e. Seasonale) has shown that the withdrawal bleeding intervals can be decreased.

Monophasic

These are typically given as 21 tablets of estrogen and progestogen, followed by seven tablets of placebo or an iron supplement,[3] [4] although some newer formulations contain more active tablets and fewer placebos. Everyday regimens (Microgynon 30 ED, Femodene ED, Logynon ED), which include seven inactive placebo pills, are rarely used in UK practice.[5] Different formulations contain different amounts of estrogen and progestogen:

Multiphasic

Progestogen-only pills

Progestogen-only pills (POPs) use a progestogen alone with doses taken continuously and no or a short gap between packs taken. People who use them may experience irregular light bleeds, and whilst irregular in the first few months of taking, usually settles to a regular pattern in time.

The following progestogens are used:

Contraindications

Generally oral contraceptives should not be used in people who currently have the following conditions:

More comprehensive guidelines that include analysis of risks and benefits can be found in the World Health Organization Medical Eligibility for Contraceptive Use Guidelines[12] which are reflected in the CDC Medical Eligibility for Contraceptive Use Guidelines.[13]

See also

Notes and References

  1. Book: Hatcher, Robert A. . Nelson, Anita . Hatcher . Robert A. . 2004 . Combined Hormonal Contraceptive Methods . Contraceptive Technology . 18th rev. . 391–460 . New York . Ardent Media . 0-9664902-5-8.
  2. Book: Speroff, Leon . Darney, Philip D. . 2005 . Oral Contraception . A Clinical Guide for Contraception . 4th . 21–138 . Philadelphia . Lippincott Williams & Wilkins . 0-7817-6488-2.
  3. US Patent:Oral contraceptive:Patent 6451778 Issued on September 17, 2002 Estimated Expiration Date: July 2, 2017. . PatentStorm LLC . 2010-11-19 . dead . https://web.archive.org/web/20110613020809/http://www.patentstorm.us/patents/6451778/description.html . June 13, 2011 .
  4. Web site: Iron deficiency in Europe . Serge Herceberg . Paul Preziosi . Pilar Galan . Public Health Nutrition: 4(2B) . 537–545 . 2010-11-19 . https://web.archive.org/web/20110726170714/http://www.idpas.org/pdf/1174IronDeficiencyinEurope.pdf . 2011-07-26 . dead .
  5. Web site: FFPRHC . 2007 . Clinical Guidance: First Prescription of Combined Oral Contraception . 2007-07-07 . dead . https://web.archive.org/web/20070704044305/http://www.ffprhc.org.uk/admin/uploads/FirstPrescCombOralContJan06.pdf . 2007-07-04 . Royal College of Obstetricians and Gynaecologists .
  6. Web site: Archived copy . 2011-04-20 . https://web.archive.org/web/20110722130555/http://www.bayerscheringpharma.es/ebbsc/cms/es/_galleries/download/s_mujer/prospectos/MelodeneS.pdf . 2011-07-22 . dead .
  7. Web site: Archived copy . 2014-11-29 . 2015-05-03 . https://web.archive.org/web/20150503060638/http://www.bayerpharma.com.br/html/bulas/publico_geral/Femiane.pdf . dead .
  8. Web site: Amorest 28. FASS.se. 2019-08-08.
  9. Web site: GoodRx - Error. 31 August 2016.
  10. Web site: Natazia Prescribing Information . 2011-12-01 . https://web.archive.org/web/20111005031047/http://berlex.bayerhealthcare.com/html/products/pi/natazia_pi.pdf . 2011-10-05 . dead .
  11. Web site: Summary of Product Characteristics for Qlaira . 2009-12-29 . 2009-12-26 . https://web.archive.org/web/20091226130117/http://emc.medicines.org.uk/medicine/21700/SPC/Qlaira . dead .
  12. Web site: Medical eligibility criteria for contraceptive use. World Health Organization. en-GB. 2016-03-11.
  13. Web site: United States Medical Eligibility Criteria (USMEC) for Contraceptive Use Unintended Pregnancy Reproductive Health CDC. www.cdc.gov. 2016-03-11.

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