Oral contraceptive formulations

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Oral contraceptives come in a variety of formulations. The main division is between combined oral contraceptive pills, containing both estrogen and synthetic progestogens, and progestogen only pills (mini-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.

How they work

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

Combined oral contraceptive pills

All contain an estrogen, ethinylestradiol or mestranol (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) although in varying amounts, and one of a number of different progestogens. They are usually taken for 21 days with then a 7 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 (only one dose of estrogen and progestogen during the 21 days) or multiphasic (varying doses). The introduction of extended-cycle monophasic pills (i.e. Seasonale) has shown that the menstrual intervals can be decreased.

Monophasic

These are typically given as 21 tablets of estrogen and progestogen, followed by 7 tablets of placebo or an iron supplement, although some newer formulations contain more active tablets and fewer placebos. Different formulations contain different amounts of estrogen and progestogen:

• 20 µg ethinylestradiol
  • 100 µg levonorgestrel (US: Alesse, Lutera, Levline)
  • 1000 µg norethindrone acetate (UK: Loestrin 20, US: Loestrin 1/20 Fe, US: Loestrin 24 Fe, Microgestin 1/20)
  • 150 µg desogestrel (UK: Mercilon)
  • 75 µg gestodene (UK: Femodette)
  • 3000 µg drospirenone (US: Yaz, Berlex)
• 30 µg ethinylestradiol
  • 150 µg levonorgestrel (UK: Microgynon 30, Ovranette, US: Levlen, Levora, Nordette)
  • 150 µg levonorgestrel – extended cycle: 84 days + 7 days placebo (US: Seasonale, Duramed)
  • 150 µg levonorgestrel – extended cycle: 84 days + 7 days 10 µg ethinylestradiol replacing placebo (US: Seasonique, Duramed)
  • 250 µg levonorgestrel (UK: Eugynon 30)
  • 300 µg norgestrel (US: Lo-Ovral)
  • 150 µg desogestrel (US: Desogen, Organon International; Ortho-Cept, Ortho-McNeil)
  • 1500 µg norethindrone acetate (UK: Loestrin 30, US: Loestrin 1.5/30, Microgestin 1.5/30)
  • 3000 µg drospirenone (US: Yasmin, Berlex)
  • 75 µg gestodene (UK: Minulet)
• 35 µg ethinylestradiol
  • 250 µg norgestimate (US: Ortho-Cyclen)
  • 400 µg norethindrone (US: Ovcon-35, Warner Chilcott)
  • 500 µg norethindrone (UK: Brevinor, Ovysmen, US: Modicon, Brevicon)
  • 1000 µg norethindrone (UK: Norimin, US: Ortho-Novum 1/35, Necon, Norethin, Norinyl 1/35)
  • 1000 µg ethynodiol diacetate (US: Demulen 1/35, Zovia 1/35E)
• 50 µg ethinylestradiol
  • 1000 µg norethindrone (US: Ovcon 50, Warner Chilcott)
  • 500 µg norgestrel (US: Ogestrel, Ovral)
  • 1000 µg ethynodiol diacetate (US: Demulen 1/50, Zovia 1/50E)
• 50 µg mestranol (equivalent to 35 µg ethinylestradiol)
  • 1000 µg norethindrone (UK: Norinyl-1, US: Necon 1/50, Norinyl 1/50,Ortho-Novum 1/50)

Multiphasic

• ethinylestradiol/desogestrel combination with 21 tablets 20 µg/150 µg, 5 tablets 10 µg/0 µg, followed by 2 tablets of placebo (US: Kariva, Barr Laboratories; Mircette, Organon)
• ethinylestradiol/desogestrel combination with 7 tablets 25 µg/100 µg, 7 tablets 25 µg/125 µg, 7 tablets 25 µg/150 µg, followed by 7 tablets of ferric oxide (US: Cyclessa, Organon; Velivet, Barr Laboratories)
• ethinylestradiol/gestodene combination with 6 tablets 30 µg/50 µg, 5 tablets 40 µg/70 µg, 10 tablets 30 µg/100 µg (UK: Triadene, Tri-Minulet)
• ethinylestradiol/levonorgestrel combination with 6 tablets 30 µg/50 µg, 5 tablets 40 µg/75 µg, 10 tablets 30 µg/125 µg (UK: Logynon, Trinordiol or with additional 7 placebo tablets as Logynon ED, US: TriLevlen, Triphasil, Trivora)
• ethinylestradiol/norethindrone combination with 10 tablets 35 µg/500 µg, 11 tablets 35 µg/1000 µg, followed by 7 tablets of placebo (US: Ortho-Novum 10/11)
• ethinylestradiol/norethindrone combination with 7 tablets 35 µg/500 µg, 14 tablets 35 µg/1000 µg (UK: BiNovum)
• ethinylestradiol/norethindrone combination with 7 tablets 35 µg/500 µg, 7 tablets 35 µg/750 µg, 7 tablets 35 µg/1000 µg, followed by 7 tablets of placebo (UK: TriNovum, US: Ortho-Novum 7/7/7)
• ethinylestradiol/norethindrone combination with 7 tablets 35 µg/500 µg, 9 tablets 35 µg/1000 µg, 5 tablets 35 µg/500 µg (UK: Synphase)
• ethinylestradiol/norgestimate combination with 7 tablets 35 µg/180 µg, 7 tablets 35 µg/215 µg, 7 tablets 35 µg/250 µg followed by 7 placebos (Ortho Tri Cyclen)
• ethinylestradiol/norgestimate combination with 7 tablets 25 µg/180 µg, 7 tablets 25 µg/215 µg, 7 tablets 25 µg/250 µg followed by 7 placebos (Ortho Tri Cyclen Lo)

Progestogen only pills

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

The following progestogens are used:

• 75 µg desogestrel (UK: Cerazette)
• 500 µg ethynodiol diacetate (UK: Femulen)
• 350 µg norethindrone (UK: Micronor, Noriday US:Micronor, Nor-QD)
• 30 µg levonorgestrel (UK: Microval, Norgeston))
• 75 µg norgestrel (UK: Neogest US:Ovrette)

Controversy

In February of 2007, the consumer advocacy group Public Citizen released a petition requesting that the FDA ban oral contraceptives containing desogestrel, citing studies going as far back as 1995 that suggest the risk of dangerous blood clots is doubled for women on such pills in comparison to other oral contraceptives. Desogestrel-containing birth control pills are sometimes referred to as “third generation” oral contraceptives. Drugs cited specifically in the petition include Apri-28, Cyclessa, Desogen, Kariva, Mircette, Ortho-Cept, Reclipsen, Velivet and some generic pills. Birth control pills that are considered “second generation” (Ortho Tri-Cyclen, for example) contain low-dose hormones and lack desogestrel.