Article: Oral contraceptive formulations

Oral contraceptives come in a variety of formulations. The main division is between combined oral contraceptive pills, containing both estrogen and synthetic progesterones (strictly progestins, but the former term is used in medical conext), and progesterone 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 progesterone 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 progesterone-only pills also thin the lining of the uterus. In theory, this could prevent pregnancy by interfering with implantation of a fertilized egg.

Combined oral contraceptive pills

All contain the estrogen ethinylestradiol, although in varying amounts, and one of a number of different progesterones. They are 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 progesterone during the 21 days) or multiphasic (varying doses).

Monophasic

These are typically given as 21 tablets of estrogen and progesterones, 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 progesterone:

• 20 µg estrogen
  • 100 µg levonorgestrel (US: Alesse®, Levline®)
  • 1000 µg norethindrone acetate (UK: Loestrin 20®, US: Loestrin 1/20®Fe, US: Loestrin 24®Fe)
  • 150 µg desogestrel (UK: Mercilon®)
  • 75 µg gestodene (UK: Femodette®)
• 30 µg estrogen
  • 150 µg levonorgestrel (UK: Microgynon 30®, Ovranette®, US: Levlen®, Levora®, Nordette®)
  • 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)
  • 3000 µg drospirenone (US: Yasmin®)
  • 75 µg gestodene (UK: Minulet®)
• 35 µg estrogen
  • 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 estrogen
  • 400 µg norethindrone (US: Ovcon-50®, Warner Chilcott))
  • 1000 µg norethindrone (US: Necon 1/50®, Norinyl 1/50®, Ortho-Novum 1/50®, Ovcon-50®)
  • 500 µg norgestrel (US: Ovral®)
  • 1000 µg ethynodiol diacetate (US: Demulen 1/50®, Zovia 1/50E®)

• 50 µg Mestranol
  • 1000 µg norethindrone (UK: Norinyl-I®)

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®)
• 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®)

Progesterone only pills

Progesterone only pills (POPs) use progesterone 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 progesterones 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®))
• 75,000 µg norgestrel (UK: Neogest® US:Ovrette®)