Birth control pill formulations

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, 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 ÃÂ¼g of mestranol is equivalent to only 35 ÃÂ¼g of ethinylestradiol and should not be used when high-dose [50 ÃÂ¼g 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.

In 2023, the combination ethinylestradiol/norgestrel was the 282nd most commonly prescribed medication in the United States, with more than 700,000 prescriptions.

Monophasic

These are typically given as 21 tablets of estrogen and progestogen, followed by seven tablets of placebo or an iron supplement, 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. Different formulations contain different amounts of estrogen and progestogen:

15 ÃÂ¼g ethinylestradiol
60 ÃÂ¼g gestodene: 24 days + 4 days placebo (Spain: Melodene-15; Israel: Minesse)
20 ÃÂ¼g ethinylestradiol
1000 ÃÂ¼g norethisterone acetate (UK: Loestrin 20, Galen; US: Loestrin 1/20, Duramed; Microgestin 1/20, Watson Pharmaceuticals; Junel 1/20, Barr)
1000 ÃÂ¼g norethisterone acetate: 24 days + 4 days ferrous fumarate only (US: Loestrin 24 Fe, Warner Chilcott)
90 ÃÂ¼g levonorgestrel: continuous: 365 days/year, no placebo (US: Amethyst, Watson)
100 ÃÂ¼g levonorgestrel: extended cycle: 84 days + 7 days 10 ÃÂ¼g ethinylestradiol only (US: LoSeasonique, Teva; CamreseLo, Teva)
100 ÃÂ¼g levonorgestrel (US: Alesse, Wyeth; Aviane, Barr; Lessina, Barr; Lutera, Watson; Sronyx, Watson)
150 ÃÂ¼g desogestrel (UK: Mercilon, Organon; HU: Novynette, Richter Gedeon)
75 ÃÂ¼g gestodene (UK: Femodette, Bayer; RU: Logest, Bayer; Brazil: Femiane, Bayer)
3000 ÃÂ¼g drospirenone: 24 days + 4 days placebo (US, EU, RU: Yaz; Bayer Schering Pharma AG. Cleonita); 21 days + 7 days placebo (US, EU: , Bayer); 24 days + 4 days placebo and levomefolate calcium (RU: Yaz Plus, US: Beyaz; Bayer)
30 ÃÂ¼g ethinylestradiol
1500 ÃÂ¼g norethisterone acetate (UK: Loestrin 30, Galen; US: Loestrin 1.5/30, Duramed; Microgestin 1.5/30, Watson; Junel 1.5/30, Barr)
300 ÃÂ¼g norgestrel (US: Lo/Ovral, Wyeth; Low-Ogestrel, Watson; Cryselle, Barr)
150 ÃÂ¼g levonorgestrel (UK: Ovranette, Wyeth; Microgynon 30, Microgynon 30 ED, Bayer; US: Nordette, Duramed, Levora, Watson, Portia, Barr)
150 ÃÂ¼g levonorgestrel: 21 day cycle + 7 days no pills (Canada: Min-Ovral 21; EU: Ovoplex 150/30; Sweden: , )
150 ÃÂ¼g levonorgestrel: 21 day cycle + 7 days placebo (Canada: Min-Ovral 28; Sweden: ; RU: Rigevidon 21+7, Richter Gedeon)
150 ÃÂ¼g levonorgestrel: extended cycle: 84 days + 7 days placebo (US: Seasonale, Duramed; Quasense, Watson; Jolessa, Barr, Introvale)
150 ÃÂ¼g levonorgestrel: extended cycle: 84 days + 7 days 10 ÃÂ¼g ethinylestradiol only (US: Seasonique, Duramed; Camrese, Teva; Amethia, Watson)
75 ÃÂ¼g gestodene (UK: Femodene, Femodene ED, Bayer; Minulet, Wyeth; RU: Femoden, Jenapharm)
150 ÃÂ¼g desogestrel (AU, EU, RU, UK: Marvelon, BR: Microdiol, US: Desogen, MSD; US: Ortho-Cept, Ortho-McNeil; RU: Regulon, Richter Gedeon)
3000 ÃÂ¼g drospirenone (AU, EU, US: Yasmin, FR: Jasmine, RU: Yarina, Bayer Schering Pharma AG); with levomefolate calcium (US: Safyral, Bayer Schering Pharma AG)
2000 ÃÂ¼g chlormadinone acetate (EU: Belara, Benelux: Bellina; Gedeon Richter)
2000 ÃÂ¼g dienogest (AU, EU: Valette, RU: Jeanine, Bayer Schering Pharma AG; RU: Siluet, Gedeon Richter)
35 ÃÂ¼g ethinylestradiol
400 ÃÂ¼g norethisterone: chewable, spearmint flavor (US: Femcon Fe, Warner Chilcott)
400 ÃÂ¼g norethisterone (US: Ovcon 35, Warner Chilcott; Balziva, Barr)
500 ÃÂ¼g norethisterone (UK: Ovysmen, Janssen-Cilag; Brevinor, Pfizer; US: Modicon, Ortho-McNeil; Brevicon, Watson; Nortrel 0.5/35, Barr)
1000 ÃÂ¼g norethisterone (AU, CAN: Synphasic, Pfizer; UK: Norimin, Pfizer; US: Ortho-Novum 1/35, Ortho-McNeil; Norinyl 1/35, Watson; Necon, Watson; Nortrel 1/35, Barr)
1000 ÃÂ¼g etynodiol diacetate (US: Demulen 1/35, Pfizer; Zovia 1/35, Watson; Kelnor, Barr)
250 ÃÂ¼g norgestimate (UK: Cilest, Janssen-Cilag; US: Ortho Cyclen, Ortho-McNeil; MonoNessa, Watson; Sprintec, Barr; Sweden: )
2000 ÃÂ¼g cyproterone acetate: only approved for severe acne or severe hirsutism in the UK (AU, RU: Diane-35, UK: Dianette, Bayer)
50 ÃÂ¼g mestranol (equivalent to 35 ÃÂ¼g ethinylestradiol)
1000 ÃÂ¼g norethisterone (UK: Norinyl-1, Pfizer; US: Ortho-Novum 1/50; Ortho-McNeil; Norinyl 1/50, Watson; Necon 1/50, Watson)
50 ÃÂ¼g ethinylestradiol
1000 ÃÂ¼g norethisterone (US: Ovcon 50, Warner Chilcott)
1000 ÃÂ¼g etynodiol diacetate (US: Demulen 1/50, Pfizer; Zovia 1/50, Watson)
500 ÃÂ¼g norgestrel (US: Ogestrel, Watson)
250 ÃÂ¼g levonorgestrel (US: Nordiol, Wyeth)
1.5 mg estradiol (as hemihydrate)
2.5 mg nomegestrol acetate: 24-day cycle + 4 placebo pills (AU, EU, RU: Zoely, MSD)
15 mg estetrol monohydrate (equivalent to 14.2 mg estetrol)
3 mg drospirenone: 24-day cycle + 4 inactive pills (US, CAN: Nexstellis, Mayne, EU: Drovelis, Gedeon Richter Plc., EU: Lydisilka, Estetra SRL)

Multiphasic

25 ÃÂ¼g ethinylestradiol: triphasic
ethinylestradiol/norgestimate combination with 7 tablets 25 ÃÂ¼g/180 ÃÂ¼g, 7 tablets 25 ÃÂ¼g/215 ÃÂ¼g, 7 tablets 25 ÃÂ¼g/250 ÃÂ¼g followed by 7 placebos (Ortho Tri-Cyclen Lo from Ortho-McNeil, Tri-Lo Sprintec back from Teva, Tri-Lo Marzia from Lupin, and norgestimate/ethinylestradiol from Mylan)
ethinylestradiol/desogestrel combination with 7 tablets 25 ÃÂ¼g/100 ÃÂ¼g, 7 tablets 25 ÃÂ¼g/125 ÃÂ¼g, 7 tablets 25 ÃÂ¼g/150 ÃÂ¼g, followed by 7 tablets of ferric oxide (US: Cyclessa, Organon; Velivet, Barr)
20/30/35 ÃÂ¼g ethinylestradiol: estrophasic
ethinylestradiol/norethisterone acetate combination with 5 tablets 20 ÃÂ¼g/1000 ÃÂ¼g, 7 tablets 30 ÃÂ¼g/1000 ÃÂ¼g, 9 tablets 35 ÃÂ¼g/1000 ÃÂ¼g, followed by 7 tablets of ferrous fumarate 75 mg (US: Estrostep Fe, Warner Chilcott)
35/30/30 ÃÂ¼g ethinylestradiol: triphasic
ethinylestradiol/desogestrel combination with 7 tablets 35 ÃÂ¼g/50 ÃÂ¼g, 7 tablets 30 ÃÂ¼g/100 ÃÂ¼g, 7 tablets 30 ÃÂ¼g/150 ÃÂ¼g (RU: Tri-Merci, Organon)
30/40/30 ÃÂ¼g ethinylestradiol: triphasic
ethinylestradiol/levonorgestrel combination with 6 tablets 30 ÃÂ¼g/50 ÃÂ¼g, 5 tablets 40 ÃÂ¼g/75 ÃÂ¼g, 10 tablets 30 ÃÂ¼g/125 ÃÂ¼g (UK: Trinordiol, Wyeth; Logynon, Logynon ED, Bayer; US: Triphasil, Wyeth; Trivora, Watson; , Barr)
ethinylestradiol/gestodene combination with 6 tablets 30 ÃÂ¼g/50 ÃÂ¼g, 5 tablets 40 ÃÂ¼g/70 ÃÂ¼g, 10 tablets 30 ÃÂ¼g/100 ÃÂ¼g (UK: Triadene, Bayer; Tri-Minulet, Wyeth)
35 ÃÂ¼g ethinylestradiol: triphasic
ethinylestradiol/norethisterone combination with 7 tablets 35 ÃÂ¼g/500 ÃÂ¼g, 9 tablets 35 ÃÂ¼g/1000 ÃÂ¼g, 5 tablets 35 ÃÂ¼g/500 ÃÂ¼g (UK: Synphase, Pfizer; US: Tri-Norinyl, Watson; Leena, Watson)
ethinylestradiol/norethisterone combination with 7 tablets 35 ÃÂ¼g/500 ÃÂ¼g, 7 tablets 35 ÃÂ¼g/750 ÃÂ¼g, 7 tablets 35 ÃÂ¼g/1000 ÃÂ¼g (UK: TriNovum, Janssen-Cilag; US: Ortho-Novum 7/7/7, Ortho-McNeil; Necon 7/7/7, Watson; Nortrel 7/7/7, Barr)
ethinylestradiol/norgestimate combination with 7 tablets 35 ÃÂ¼g/180 ÃÂ¼g, 7 tablets 35 ÃÂ¼g/215 ÃÂ¼g, 7 tablets 35 ÃÂ¼g/250 ÃÂ¼g followed by 7 placebos (Ortho Tri-Cyclen, Ortho-McNeil; TriNessa, Watson; Tri-Sprintec, Barr)
35 ÃÂ¼g ethinylestradiol: biphasic
ethinylestradiol/norethisterone combination with 10 tablets 35 ÃÂ¼g/500 ÃÂ¼g, 11 tablets 35 ÃÂ¼g/1000 ÃÂ¼g, followed by 7 placebos (US: Ortho-Novum 10/11, Ortho-McNeil; Necon 10/11, Watson)
ethinylestradiol/norethisterone combination with 7 tablets 35 ÃÂ¼g/500 ÃÂ¼g, 14 tablets 35 ÃÂ¼g/1000 ÃÂ¼g (UK: BiNovum, Janssen-Cilag)

3/2/1 mg estradiol valerate: estrophasic
estradiol valerate/dienogest combination with 2 tablets 3 mg/0 mg, followed by 5 tablets 2 mg/2 mg, 17 tablets 2 mg/3 mg, 2 tablets 1 mg/0 mg, and 2 placebos. (AU, EU, RU: Qlaira, US: Natazia, Bayer)

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:

350 ÃÂ¼g norethisterone (norethindrone) (UK: Micronor, Janssen-Cilag; Noriday, Pfizer; US: Micronor, Ortho-McNeil; Nor-QD, Watson; Nora-BE, Watson; Jolivette, Watson; Camila, Barr; Errin, Barr; Heather, Glenmark; RU: Primolut-Nor, Bayer; Norkolut, Richter Gedeon)
4 mg drospirenone (Slynd)
75 ÃÂ¼g desogestrel (UK: Cerazette, Loestrin; RU: Cerazette, Organon; Lactinette, Richter Gedeon; SE: Gestrina)
30 ÃÂ¼g levonorgestrel (UK: Norgeston, Bayer; AUS, RU: Microlut, Bayer)
500 ÃÂ¼g etynodiol diacetate (UK: Femulen, Pfizer)
500 ÃÂ¼g lynestrenol (RU: Exluton, Organon)
75 ÃÂ¼g norgestrel (US: Opill, Perrigo)

Contraindications

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

Thrombophlebitis or thromboembolic disorders
A history of deep vein thrombophlebitis or thromboembolic disorders
Cerebrovascular or coronary artery disease (current or history)
Valvular heart disease with thrombogenic complications
Severe hypertension
Diabetes with vascular involvement
Headaches with focal neurological symptoms
Major surgery with prolonged immobilization
Known or suspected carcinoma of the breast or personal history of breast cancer
Carcinoma of the endometrium or other known or suspected estrogen-dependent neoplasia
Undiagnosed abnormal genital bleeding
Cholestatic jaundice of pregnancy or jaundice with prior pill use
Hepatic adenomas or carcinomas, or active liver disease
Known or suspected pregnancy
Hypersensitivity to any component of the product

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

References