Norethisterone acetate

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Norethisterone acetate
Norethisterone acetate.svg
Norethisterone acetate molecule ball.png
Clinical data
Trade namesPrimolut-Nor, Aygestin, Gestakadin, Milligynon, Monogest, Norlutate, Primolut N, SH-420, Sovel, Styptin, others
Other namesNETA; NETAc; Norethindrone acetate; SH-420; 17α-Ethynyl-19-nortestosterone 17β-acetate; 17α-Ethynylestra-4-en-17β-ol-3-one 17β-acetate
AHFS/Drugs.comInternational Drug Names
Routes of
By mouth
Drug classProgestogen; Progestin; Progestogen ester
ATC code
Legal status
Legal status
  • In general: ℞ (Prescription only)
  • (8R,9S,10R,13S,14S,17S)-17-ethynyl-13-methyl-3-oxo-2,3,6,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-17-yl acetate
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.000.121 Edit this at Wikidata
Chemical and physical data
Molar mass340.463 g·mol−1
3D model (JSmol)
  • CC(=O)O[C@]1(CC[C@@H]2[C@@]1(CC[C@H]3[C@H]2CCC4=CC(=O)CC[C@H]34)C)C#C
  • InChI=1S/C22H28O3/c1-4-22(25-14(2)23)12-10-20-19-7-5-15-13-16(24)6-8-17(15)18(19)9-11-21(20,22)3/h1,13,17-20H,5-12H2,2-3H3/t17-,18+,19+,20-,21-,22-/m0/s1 ☒N

Norethisterone acetate (NETA), also known as norethindrone acetate and sold under the brand name Primolut-Nor among others, is a progestin medication which is used in birth control pills, menopausal hormone therapy, and for the treatment of gynecological disorders.[1][2][3][4] The medication available in low-dose and high-dose formulations and is used alone or in combination with an estrogen.[5][4][6][7] It is taken by mouth.[6]

Side effects of NETA include menstrual irregularities, headaches, nausea, breast tenderness, mood changes, acne, increased hair growth, and others.[6] NETA is a progestin, or a synthetic progestogen, and hence is an agonist of the progesterone receptor, the biological target of progestogens like progesterone.[1] It has weak androgenic and estrogenic activity and no other important hormonal activity.[1][8] The medication is a prodrug of norethisterone in the body.[9][10]

NETA was patented in 1957 and was introduced for medical use in 1964.[11][12] It is sometimes referred to as a "first-generation" progestin.[13][14] NETA is marketed widely throughout the world.[4] It is available as a generic medication.[15]

Medical uses[edit]

NETA is used as a hormonal contraceptive in combination with estrogen, in the treatment of gynecological disorders such as abnormal uterine bleeding, and as a component of menopausal hormone therapy for the treatment of menopausal symptoms.[4]

Available forms[edit]

NETA is available in the form of tablets for use by mouth both alone and in combination with estrogens including estradiol, estradiol valerate, and ethinylestradiol.[16][4] Transdermal patches providing a combination of 50 μg/day estradiol and 0.14 or 0.25 mg/day NETA are available under the brand names CombiPatch and Estalis.[16][4]

NETA was previously available for use by intramuscular injection in the form of ampoules containing 20 mg NETA, 5 mg estradiol benzoate, 8 mg estradiol valerate, and 180 mg testosterone enanthate in oil solution under the brand name Ablacton to suppress lactation in postpartum women.[17][18][19][20]


Side effects[edit]

Side effects of NETA include menstrual irregularities, headaches, nausea, breast tenderness, mood changes, acne, increased hair growth, and others.[6]




Norethisterone (17β-deacetyl-NETA), the active form of NETA.
Norethisterone and ethinylestradiol levels over 24 hours after a single oral dose of 10 mg NETA in postmenopausal women.[21]

NETA is a prodrug of norethisterone in the body.[9] Upon oral ingestion, it is rapidly converted into norethisterone by esterases during intestinal and first-pass hepatic metabolism.[10] Hence, as a prodrug of norethisterone, NETA has essentially the same effects, acting as a potent progestogen with additional weak androgenic and estrogenic activity (the latter via its metabolite ethinylestradiol).[1][8]

In terms of dosage equivalence, norethisterone and NETA are typically used at respective dosages of 0.35 mg/day and 0.6 mg/day as progestogen-only contraceptives, and at respective dosages of 0.5–1 mg/day and 1–1.5 mg/day in combination with ethinylestradiol in combined oral contraceptives.[8] Conversely, the two drugs have been used at about the same dosages in menopausal hormone therapy for the treatment of menopausal symptoms.[8] NETA is of about 12% higher molecular weight than norethisterone due to the presence of its C17β acetate ester.[2]

Micronization of NETA has been found to increase its potency by several-fold in animals and women.[22][23][24][25] The endometrial transformation dosage of micronized NETA per cycle is 12 to 14 mg, whereas that for non-micronized NETA is 30 to 60 mg.[22]

NETA metabolizes into ethinylestradiol at a rate of 0.20 to 0.33% across a dose range of 10 to 40 mg.[26][27] Peak levels of ethinylestradiol with a 10, 20, or 40 mg dose of NETA were 58, 178, and 231 pg/mL, respectively.[26][27] For comparison, a 30 to 40 μg dose of oral ethinylestradiol typically results in a peak ethinylestradiol level of 100 to 135 pg/mL.[27] As such, in terms of ethinylestradiol exposure, 10 to 20 mg NETA may be equivalent to 20 to 30 μg ethinylestradiol and 40 mg NETA may be similar to 50 μg ethinylestradiol.[27] Due to its estrogenic activity via ethinylestradiol, high doses of NETA have been proposed for add-back in the treatment of endometriosis without estrogen supplementation.[26] Generation of ethinylestradiol with high doses of NETA may increase the risk of venous thromboembolism.[27]

Relative affinities (%) of norethisterone, metabolites, and prodrugs
Compound Typea PR AR ER GR MR SHBG CBG
Norethisterone 67–75 15 0 0–1 0–3 16 0
5α-Dihydronorethisterone Metabolite 25 27 0 0 ? ? ?
3α,5α-Tetrahydronorethisterone Metabolite 1 0 0–1 0 ? ? ?
3α,5β-Tetrahydronorethisterone Metabolite ? 0 0 ? ? ? ?
3β,5α-Tetrahydronorethisterone Metabolite 1 0 0–8 0 ? ? ?
Ethinylestradiol Metabolite 15–25 1–3 112 1–3 0 0.18 0
Norethisterone acetate Prodrug 20 5 1 0 0 ? ?
Norethisterone enanthate Prodrug ? ? ? ? ? ? ?
Noretynodrel Prodrug 6 0 2 0 0 0 0
Etynodiol Prodrug 1 0 11–18 0 ? ? ?
Etynodiol diacetate Prodrug 1 0 0 0 0 ? ?
Lynestrenol Prodrug 1 1 3 0 0 ? ?
Notes: Values are percentages (%). Reference ligands (100%) were promegestone for the PR, metribolone for the AR, estradiol for the ER, dexamethasone for the GR, aldosterone for the MR, dihydrotestosterone for SHBG, and cortisol for CBG. Footnotes: a = Active or inactive metabolite, prodrug, or neither of norethisterone. Sources: See template.


NETA, also known as norethinyltestosterone acetate, as well as 17α-ethynyl-19-nortestosterone 17β-acetate or 17α-ethynylestra-4-en-17β-ol-3-one 17β-acetate, is a progestin, or synthetic progestogen, of the 19-nortestosterone group, and a synthetic estrane steroid.[2][5] It is the C17β acetate ester of norethisterone.[2][5] NETA is a derivative of testosterone with an ethynyl group at the C17α position, the methyl group at the C19 position removed, and an acetate ester attached at the C17β position.[2][5] In addition to testosterone, it is a combined derivative of nandrolone (19-nortestosterone) and ethisterone (17α-ethynyltestosterone).[2][5]


Chemical syntheses of NETA have been published.[28]


Schering AG filed for a patent for NETA in June 1957, and the patent was issued in December 1960.[11] The drug was first marketed, by Parke-Davis as Norlestrin in the United States, in March 1964.[11][12] This was a combination formulation of 2.5 mg NETA and 50 μg ethinylestradiol and was indicated as an oral contraceptive.[11][12] Other early brand names of NETA used in oral contraceptives included Minovlar and Anovlar.[11]

Society and culture[edit]

Generic names[edit]

Norethisterone acetate is the INN, BANM, and JAN of NETA while norethindrone acetate is its USAN and USP.[2][5][4]

Brand names[edit]

NETA is marketed under a variety of brand names throughout the world including Primolut-Nor (major), Aygestin (US), Gestakadin, Milligynon, Monogest, Norlutate (US, CA), Primolut N, SH-420 (UK), Sovel, and Styptin among others.[2][5][4]

Formulations and brand names of norethisterone and esters
Composition Dose Brand names Use
NET only Low (e.g., 0.35 mg) Multiple[a] Progestogen-only oral contraceptive
NET or NETA only High (e.g., 5 mg, 10 mg) Multiple[b] Gynecological disorders and other uses
NETE only Injection (e.g., 200 mg) Multiple[c] Progestogen-only injectable contraceptive
NET or NETA with ethinylestradiol Low (e.g., 0.4 mg, 0.5 mg, 0.75 mg, 1 mg, 1.5 mg) Multiple[d] Combined oral contraceptive
NET with mestranol Low (e.g., 1 mg, 2 mg) Multiple[e] Combined oral contraceptive
NETA with estradiol Low (e.g., 0.1 mg, 0.5 mg) Multiple[f] Combined menopausal hormone therapy
NETE with estradiol valerate Injection (e.g., 50 mg) Multiple[g] Combined injectable contraceptive
Abbreviations: NET = Norethisterone. NETA = Norethisterone acetate. NETE = Norethisterone enanthate.
Sources: [29][7][5][30]
  1. ^ Camila, Errin, Heather, Jencycla, Jolivette, Locilan, Micro-Novum, Micronovum, Micronor, Nor-QD, Nora, Noriday, Ortho Micronor
  2. ^ Aygestin, Lupaneta Pack (combination pack with leuprorelin), Norcolut, Norlutate, Primolut N, Primolut Nor, SH-420, Utovlan
  3. ^ Depocon, Doryxas, NET-EN, Noristerat, Norigest, Nur-Isterate
  4. ^ Aranelle, Balziva, Binovum, Brevicon, Brevinor, Briellyn, Cyclafem, Dasetta, Estrostep, Femcon, Generess, Gildagia, Gildess, Jinteli, Junel, Larin, Leena, Lo Loestrin, Lo Minastrin, Loestrin, Lolo, Lomedia, Microgestin, Minastrin, Modicon, Nelova, Norimin, Norinyl, Nortrel, Ortho, Ortho-Novum, Ovcon, Ovysmen, Philith, Primella, Select, Synphase, Synphasic, Tilia, Tri-Legest, Tri-Norinyl, Trinovum, Vyfemla, Wera, Wymzya, Zenchent, Zeosa
  5. ^ Norethin, Noriday, Norinyl, Norquen, Ortho-Novum, Sophia
  6. ^ Activella, Activelle, Alyacen, Cliane, Climagest, Climesse, Cliovelle, CombiPatch, Elleste Duet, Estalis, Estropause, Eviana, Evorel, Kliane, Kliofem, Kliogest, Kliovance, Mesigyna, Mesygest, Mimvey, Necon, Novofem, Nuvelle, Sequidot, Systen, Trisequens
  7. ^ Chinese Injectable No. 3, Efectimes, Ginediol, Mesigyna, Mesilar, Meslart, Mesocept, Mesygest, Nofertyl, Nofertyl Lafrancol, Noregyna, Norestrin, Norifam, Norigynon, Nostidyn, Sexseg, Solouna


United States[edit]

NETA is marketed in high-dose 5 mg oral tablets in the United States under the brand names Aygestin and Norlutate for the treatment of gynecological disorders.[31] In addition, it is available under a large number of brand names at much lower dosages (0.1 to 1 mg) in combination with estrogens such as ethinylestradiol and estradiol as a combined oral contraceptive and for use in menopausal hormone therapy for the treatment of menopausal symptoms.[7]


NETA has been studied for use as a potential male hormonal contraceptive in combination with testosterone in men.[32]

See also[edit]


  1. ^ a b c d Kuhl H (2005). "Pharmacology of estrogens and progestogens: influence of different routes of administration" (PDF). Climacteric. 8 Suppl 1: 3–63. doi:10.1080/13697130500148875. PMID 16112947. S2CID 24616324.
  2. ^ a b c d e f g h J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. pp. 886–. ISBN 978-1-4757-2085-3.
  3. ^ Index Nominum 2000: International Drug Directory. Taylor & Francis US. 2000. p. 750. ISBN 978-3-88763-075-1. Retrieved 30 May 2012.
  4. ^ a b c d e f g h
  5. ^ a b c d e f g h Index Nominum 2000: International Drug Directory. Taylor & Francis. January 2000. pp. 749–. ISBN 978-3-88763-075-1.
  6. ^ a b c d
  7. ^ a b c "Drugs@FDA: FDA Approved Drug Products". United States Food and Drug Administration. Retrieved 27 November 2016.
  8. ^ a b c d IARC Working Group on the Evaluation of Carcinogenic Risks to Humans; World Health Organization; International Agency for Research on Cancer (2007). Combined Estrogen-progestogen Contraceptives and Combined Estrogen-progestogen Menopausal Therapy. World Health Organization. pp. 417–. ISBN 978-92-832-1291-1. Norethisterone and its acetate and enanthate esters are progestogens that have weak estrogenic and androgenic properties.
  9. ^ a b Thomas L. Lemke; David A. Williams (2008). Foye's Principles of Medicinal Chemistry. Lippincott Williams & Wilkins. pp. 1316–. ISBN 978-0-7817-6879-5.
  10. ^ a b Chwalisz K, Surrey E, Stanczyk FZ (2012). "The hormonal profile of norethindrone acetate: rationale for add-back therapy with gonadotropin-releasing hormone agonists in women with endometriosis". Reprod Sci. 19 (6): 563–71. doi:10.1177/1933719112438061. PMID 22457429. S2CID 2882899.
  11. ^ a b c d e Lara Marks (2010). Sexual Chemistry: A History of the Contraceptive Pill. Yale University Press. pp. 73–. ISBN 978-0-300-16791-7.
  12. ^ a b c Robert W. Blum (22 October 2013). Adolescent Health Care: Clinical Issues. Elsevier Science. pp. 216–. ISBN 978-1-4832-7738-7.
  13. ^ Robert Anthony Hatcher; Anita L. Nelson, M.D. (2007). Contraceptive Technology. Ardent Media. pp. 195–. ISBN 978-1-59708-001-9.
  14. ^ Sulochana Gunasheela (14 March 2011). Practical Management of Gynecological Problems. JP Medical Ltd. pp. 31–. ISBN 978-93-5025-240-6.
  15. ^
  16. ^ a b James M. Rippe (15 March 2013). Lifestyle Medicine. CRC Press. pp. 280–. ISBN 978-1-4398-4544-8.
  17. ^ A. Labhart (6 December 2012). Clinical Endocrinology: Theory and Practice. Springer Science & Business Media. pp. 696–. ISBN 978-3-642-96158-8.
  18. ^ F. G. Sulman (22 October 2013). Hypothalamic Control of Lactation: Monographs on Endocrinology. Elsevier Science. pp. 184–. ISBN 978-1-4831-9303-8.
  19. ^ Ufer, Joachim (1 January 1978). Hormontherapie in der Frauenheilkunde: Grundlagen und Praxis [Hormone Therapy in Gynecology: Principles and Practice] (in German) (5 ed.). de Gruyter. ISBN 978-3110066647. OCLC 924728827.
  20. ^ Drugs. S. Karger. 1975. p. 128. 5.5.4 Oestradiol valerate + Benzoate/Testosterone Enanthate/Norethisterone Acetate (Ablacton). This product contains oestradiol benzoate 5mg, oestradiol valerate 8mg, norethisterone acetate 20mg and testosterone enanthate 180mg in a 1ml oily solution. It is injected intramuscularly.
  21. ^ Kuhnz W, Heuner A, Hümpel M, Seifert W, Michaelis K (1997). "In vivo conversion of norethisterone and norethisterone acetate to ethinyl etradiol in postmenopausal women". Contraception. 56 (6): 379–85. doi:10.1016/s0010-7824(97)00174-1. PMID 9494772. [...] it has been shown that the repeated oral administration of NET at doses of 0.5 to 3.0 mg to fertile women caused a dose related decrease in the serum levels of SHBG.24 It should be borne in mind that, besides its progestational activity, NET is also characterized by a marked androgenic partial activity, which has a suppressive effect on the synthesis of SHBG and therefore compensates the effects of an additional exposure to EE, on the liver.
  22. ^ a b J. Horsky; J. Presl (6 December 2012). Ovarian Function and its Disorders: Diagnosis and Therapy. Springer Science & Business Media. pp. 313–. ISBN 978-94-009-8195-9.
  23. ^ Janet Brotherton (1976). Sex Hormone Pharmacology. Academic Press. p. 34. ISBN 978-0-12-137250-7.
  24. ^ Gibian H, Kopp R, Kramer M, Neumann F, Richter H (1968). "Effect of particle size on biological activity of norethisterone acetate". Acta Physiol Lat Am. 18 (4): 323–6. PMID 5753386.
  25. ^ He CH, Shi YE, Liao DL, Zhu YH, Xu JQ, Matlin SA, Vince PM, Fotherby K, Van Look PF (May 1990). "Comparative cross-over pharmacokinetic study on two types of postcoital contraceptive tablets containing levonorgestrel". Contraception. 41 (5): 557–67. doi:10.1016/0010-7824(90)90064-3. PMID 2112080.
  26. ^ a b c Sitruk-Ware R, Nath A (February 2013). "Characteristics and metabolic effects of estrogen and progestins contained in oral contraceptive pills". Best Pract. Res. Clin. Endocrinol. Metab. 27 (1): 13–24. doi:10.1016/j.beem.2012.09.004. PMID 23384742.
  27. ^ a b c d e Chu MC, Zhang X, Gentzschein E, Stanczyk FZ, Lobo RA (June 2007). "Formation of ethinyl estradiol in women during treatment with norethindrone acetate". J. Clin. Endocrinol. Metab. 92 (6): 2205–7. doi:10.1210/jc.2007-0044. PMID 17341557.
  28. ^ Die Gestagene. Springer-Verlag. 27 November 2013. p. 14. ISBN 978-3-642-99941-3.
  29. ^
  30. ^ IARC Working Group on the Evaluation of Carcinogenic Risks to Humans; International Agency for Research on Cancer (1 January 1999). Hormonal Contraception and Post-menopausal Hormonal Therapy (PDF). IARC. p. 65. ISBN 978-92-832-1272-0. Lay summary.
  31. ^ "Drugs@FDA: FDA Approved Drug Products". United States Food and Drug Administration. Retrieved 6 December 2016.
  32. ^ Nieschlag E (2010). "Clinical trials in male hormonal contraception" (PDF). Contraception. 82 (5): 457–70. doi:10.1016/j.contraception.2010.03.020. PMID 20933120.