Norethisterone acetate

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 ingested orally.[6]

Norethisterone acetate
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
MedlinePlusa604034
Routes of
administration		By mouth
Drug classProgestogen; Progestin; Progestogen ester
ATC code
Legal status
Legal status
  • In general: ℞ (Prescription only)
Identifiers
IUPAC name
  • (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
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard100.000.121
Chemical and physical data
FormulaC22H28O3
Molar mass340.463 g·mol−1
3D model (JSmol)
SMILES
  • 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
  • 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
  • Key:IMONTRJLAWHYGT-ZCPXKWAGSA-N N
  (verify)

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

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

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]

Contraindications
See also: Norethisterone § Contraindications, and Progestin § Contraindications

Side effects
See also: Norethisterone § Side effects, and Progestin § Side effects

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

Overdose
See also: Norethisterone § Overdose, and Progestin § Overdose

Interactions
See also: Norethisterone § Interactions, and Progestin § Interactions

Pharmacology
See also: Norethisterone § Pharmacology, and Norethisterone § Pharmacokinetics

Pharmacodynamics
Norethisterone (17β-deacetyl-NETA), the active form of NETA.

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]

Relative affinities (%) of norethisterone, metabolites, and prodrugs
CompoundTypeaPRARERGRMRSHBGCBG
Norethisterone–67–751500–10–3160
5α-DihydronorethisteroneMetabolite252700 ? ? ?
3α,5α-TetrahydronorethisteroneMetabolite100–10 ? ? ?
3α,5β-TetrahydronorethisteroneMetabolite ?00 ? ? ? ?
3β,5α-TetrahydronorethisteroneMetabolite100–80 ? ? ?
EthinylestradiolMetabolite15–251–31121–300.180
Norethisterone acetateProdrug205100 ? ?
Norethisterone enanthateProdrug ? ? ? ? ? ? ?
NoretynodrelProdrug6020000
EtynodiolProdrug1011–180 ? ? ?
Etynodiol diacetateProdrug10000 ? ?
LynestrenolProdrug11300 ? ?
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.

Progestogenic effects

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.[21][22][23][24] 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.[21]

Estrogenic effects
Norethisterone and ethinylestradiol levels over 24 hours after a single oral dose of 10 mg NETA in postmenopausal women.[25]

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] In another study however, 5 mg NETA produced an equivalent of 28 μg ethinylestradiol (0.7% conversion rate) and 10 mg NETA produced an equivalent of 62 μg ethinylestradiol (1.0% conversion rate).[25][28] 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 but may also decrease menstrual bleeding relative to progestogen exposure alone.[27][28]

Antigonadotropic effects

NETA has antigonadotropic effects via its progestogenic activity and can dose-dependently suppress gonadotropin and sex hormone levels in women and men.[1][29][30][31] The ovulation-inhibiting dose of NETA is about 0.5 mg/day in women.[1] In healthy young men, NETA alone at a dose of 5 to 10 mg/day orally for 2 weeks suppressed testosterone levels from ~527 ng/dL to ~231 ng/dL (–56%).[30]

Chemistry
See also: List of progestogens, Progestogen ester, List of progestogen esters, and List of androgens/anabolic steroids

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]

Synthesis

Chemical syntheses of NETA have been published.[32]

History

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

Generic names

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

Brand names

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
CompositionDoseBrand namesUse
NET onlyLow (e.g., 0.35 mg)Multiple[lower-alpha 1]Progestogen-only oral contraceptive
NET or NETA onlyHigh (e.g., 5 mg, 10 mg)Multiple[lower-alpha 2]Gynecological disorders and other uses
NETE onlyInjection (e.g., 200 mg)Multiple[lower-alpha 3]Progestogen-only injectable contraceptive
NET or NETA with ethinylestradiolLow (e.g., 0.4 mg, 0.5 mg, 0.75 mg, 1 mg, 1.5 mg)Multiple[lower-alpha 4]Combined oral contraceptive
NET with mestranolLow (e.g., 1 mg, 2 mg)Multiple[lower-alpha 5]Combined oral contraceptive
NETA with estradiolLow (e.g., 0.1 mg, 0.5 mg)Multiple[lower-alpha 6]Combined menopausal hormone therapy
NETE with estradiol valerateInjection (e.g., 50 mg)Multiple[lower-alpha 7]Combined injectable contraceptive
Abbreviations: NET = Norethisterone. NETA = Norethisterone acetate. NETE = Norethisterone enanthate.
Sources: [33][7][5][34]
Notes:
  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
See also: List of progestogens available in the United States

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.[35] 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]

Research

NETA has been studied for use as a potential male hormonal contraceptive in combination with testosterone in men.[36]

See also

References
  1. Kuhl H (August 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. 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. "Norethindrone Monograph for Professionals".
  5. Index Nominum 2000: International Drug Directory. Taylor & Francis. January 2000. pp. 749–. ISBN 978-3-88763-075-1.
  6. https://www.accessdata.fda.gov/drugsatfda_docs/label/2007/018405s023lbl.pdf
  7. "Drugs@FDA: FDA Approved Drug Products". United States Food and Drug Administration. Retrieved 27 November 2016.
  8. 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. 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. 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. Lara Marks (2010). Sexual Chemistry: A History of the Contraceptive Pill. Yale University Press. pp. 73–. ISBN 978-0-300-16791-7.
  12. 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. "Generic Aygestin Availability".
  16. 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. 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.
  22. Janet Brotherton (1976). Sex Hormone Pharmacology. Academic Press. p. 34. ISBN 978-0-12-137250-7.
  23. 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.
  24. 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.
  25. 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.
  26. 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. 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. Vilk Ayalon N, Segev L, Samson AO, Yagel S, Cohen SM, Green T, Hochler H (June 2022). "Norethisterone Reduces Vaginal Bleeding Caused by Progesterone-Only Birth Control Pills". J Clin Med. 11 (12): 3389. doi:10.3390/jcm11123389. PMC 9224784. PMID 35743459.
  29. Endrikat J, Gerlinger C, Richard S, Rosenbaum P, Düsterberg B (December 2011). "Ovulation inhibition doses of progestins: a systematic review of the available literature and of marketed preparations worldwide". Contraception. 84 (6): 549–57. doi:10.1016/j.contraception.2011.04.009. PMID 22078182.
  30. Zitzmann M, Rohayem J, Raidt J, Kliesch S, Kumar N, Sitruk-Ware R, Nieschlag E (May 2017). "Impact of various progestins with or without transdermal testosterone on gonadotropin levels for non-invasive hormonal male contraception: a randomized clinical trial". Andrology. 5 (3): 516–526. doi:10.1111/andr.12328. PMID 28189123. S2CID 41502711.
  31. Kamischke A, Diebäcker J, Nieschlag E (September 2000). "Potential of norethisterone enanthate for male contraception: pharmacokinetics and suppression of pituitary and gonadal function". Clin Endocrinol (Oxf). 53 (3): 351–8. doi:10.1046/j.1365-2265.2000.01097.x. PMID 10971453. S2CID 70515136.
  32. Die Gestagene. Springer-Verlag. 27 November 2013. p. 14. ISBN 978-3-642-99941-3.
  33. https://www.drugs.com/international/norethisterone.html
  34. 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.
  35. "Drugs@FDA: FDA Approved Drug Products". United States Food and Drug Administration. Retrieved 6 December 2016.
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