Equilin
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| Synonyms | Δ7-Estrone; 7-Dehydroestrone; Estra-1,3,5(10),7-tetraen-3-ol-17-one |
| Routes of administration | By mouth |
| Drug class | Estrogen |
| Identifiers | |
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| DrugBank | |
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| ChEMBL | |
| ECHA InfoCard |
100.006.809  |
| Chemical and physical data | |
| Formula | C18H20O2 |
| Molar mass | 268.355 g/mol |
| 3D model (JSmol) | |
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Equilin is a naturally occurring estrogen sex hormone found in horses as well as a medication.[1][2][3] It is one of the estrogens present in the estrogen mixtures known as conjugated estrogens (CEEs; brand name Premarin) and esterified estrogens (EEs; Estratab, Menest).[2][3] CEEs is the most commonly used form of estrogen in hormone replacement therapy (HRT) for menopausal symptoms in the United States.[3] Estrone sulfate is the major estrogen in CEEs (about 50%) while equilin sulfate is the second major estrogen in the formulation, present as about 25% of the total.[2][3]
Pharmacology
Pharmacodynamics
Equilin is an estrogen, or an agonist of the estrogen receptors (ERs), the ERα and ERβ.[2] In terms of relative binding affinity for the ERs, equilin has about 13% and 49% of that of estradiol for the ERα and ERβ, respectively.[2] Analogously to the reversible transformation of estrone into estradiol by 17β-hydroxysteroid dehydrogenase, equilin can be converted into the more potent estrogen 17β-dihydroequilin in the body.[2][3] This estrogen has about 113% and 108% of the relative binding affinities of estradiol for the ERα and ERβ, respectively.[2][3] Equilin is present in CEEs in the form of equilin sulfate, which itself is inactive and acts as a prodrug of equilin via steroid sulfatase.[2][3]
Similarly to synthetic estrogens like ethinylestradiol, equilin and CEEs have disproportionate effects in certain tissues such as the liver and uterus relative to bioidentical human estrogens like estradiol and estrone.[2] Because of their disproportionate potency in the liver, equilin and CEEs have relatively increased effects on liver protein synthesis compared to estradiol.[2]
A dosage of 0.25 mg/day equilin sulfate is equivalent to 0.625 mg/day CEEs in terms of relief from hot flashes.[2] At a dosage of 0.625 mg/day equilin sulfate, the increases in circulating levels of sex hormone-binding globulin (SHBG), corticosteroid-binding globulin, and angiotensinogen were 1.5 to 8 times those observed with estrone sulfate.[2] Equilin has about 42% of the relative potency of CEEs in the vagina and 80% of the relative potency of CEEs in the uterus, while its more active form, 17β-dihydroequilin, has about 83% of the relative potency of CEEs in the vagina and 200% of the relative potency of CEEs in the uterus.[2]
| Estrogen | Type | HF | VE | UCa | FSH | LH | HDL-C | SHBG | CBG | AGT | Ratio |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Estradiol | Bioidentical | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Estrone | Bioidentical | ND | ND | ND | 0.3 | 0.3 | ND | ND | ND | ND | ND |
| Estriol | Bioidentical | 0.3 | 0.3 | 0.1 | 0.3 | ND | 0.2 | ND | ND | ND | 0.67 |
| Estrone sulfate | Bioidentical | ND | 0.9 | 0.9 | 0.9 | 0.9 | 0.5 | 0.9 | 0.7 | 1.5 | 0.56–1.7 |
| Conjugated estrogens | Natural | 1.2 | 1.5 | 2.0 | 1.1 | 1.0 | 1.5 | 3.0 | 1.5 | 5.0 | 1.3–4.5 |
| Equilin sulfate | Natural | ND | ND | ND | ND | ND | 6.0 | 7.5 | 6.0 | 7.5 | ND |
| Ethinylestradiol | Synthetic | 120 | 150 | 40 | 120 | 100 | 400 | 500 | 600 | 350 | 2.9–5.0 |
| Diethylstilbestrol | Synthetic | ND | ND | ND | 3.4 | ND | ND | 25.6 | 24.5 | 19.5 | 5.7–7.5 |
| Notes: Values are ratios, with estradiol as standard (i.e., 1.0). Abbreviations: HF = Clinical relief of hot flashes. VE = Increased proliferation of vaginal epithelium. UCa = Decrease in UCa. FSH = Suppression of FSH levels. LH = Suppression of LH levels. HDL-C, SHBG, CBG, and AGT = Increase in the serum levels of these hepatic proteins. Ratio = Ratio of liver protein effects to hot flashes relief and gonadotropin suppression. ND = No data. Type: Bioidentical = Identical to those found in humans. Natural = Naturally occurring but not identical to those found in humans (e.g., estrogens of other species). Synthetic = Man-made, does not naturally occur in animals or in the environment. Miscellaneous: Direct link to table. Sources: [2][4][5][6][7][8] | |||||||||||
Pharmacokinetics
Equilin has about 8% of the relative binding affinity of testosterone for SHBG, relative to 12% in the case of estrone.[2] In terms of plasma protein binding, it is bound 26% to SHBG and 13% to albumin.[2] The metabolic clearance rates of equilin and equilin sulfate are 2,640 L/day/m2 and 175 L/day/m2, respectively.[2] In accordance, the biological half-life of equilin sulfate is substantially longer than that of equilin.[2] Equilin is converted into 17β-dihydroequilin in the liver and in other tissues.[2][3] Equilin and 17β-dihydroequilin can also be transformed into equilenin and 17β-dihydroequilenin.[2][3] Equilin is excreted in the form of glucuronide conjugates.[2]
Chemistry
Equilin, also known as δ7-estrone or as 7-dehydroestrone, as well as estra-1,3,5(10),7-tetraen-3-ol-17-one, is a naturally occurring estrane steroid and an analogue of estrone.[2][3] In terms of chemical structure and pharmacology, equilin is to 17β-dihydroequilin (δ7-17β-estradiol) as estrone is to estradiol.[2][3]
References
- ↑ J. Elks (14 November 2014). The Dictionary of Drugs: Chemical Data: Chemical Data, Structures and Bibliographies. Springer. p. 495. ISBN 978-1-4757-2085-3.
- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 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.
- 1 2 3 4 5 6 7 8 9 10 11 Bhavnani BR, Stanczyk FZ (July 2014). "Pharmacology of conjugated equine estrogens: efficacy, safety and mechanism of action". J. Steroid Biochem. Mol. Biol. 142: 16–29. doi:10.1016/j.jsbmb.2013.10.011. PMID 24176763.
- ↑ Alfred S. Wolf; H.P.G. Schneider (12 March 2013). Östrogene in Diagnostik und Therapie. Springer-Verlag. pp. 78–. ISBN 978-3-642-75101-1.
- ↑ Manfred Kaufmann; Serban-Dan Costa; Anton Scharl (27 November 2013). Die Gynäkologie. Springer-Verlag. pp. 105–. ISBN 978-3-662-11496-4.
- ↑ Mashchak CA, Lobo RA, Dozono-Takano R, Eggena P, Nakamura RM, Brenner PF, Mishell DR (November 1982). "Comparison of pharmacodynamic properties of various estrogen formulations". Am. J. Obstet. Gynecol. 144 (5): 511–8. doi:10.1016/0002-9378(82)90218-6. PMID 6291391.
- ↑ Helgason S (1982). "Estrogen replacement therapy after the menopause. Estrogenicity and metabolic effects". Acta Obstet Gynecol Scand Suppl. 107: 1–29. doi:10.3109/00016348209155333. PMID 6282033.
- ↑ Lobo RA, Nguyen HN, Eggena P, Brenner PF (February 1988). "Biologic effects of equilin sulfate in postmenopausal women". Fertil. Steril. 49 (2): 234–8. doi:10.1016/S0015-0282(16)59708-8. PMID 3338581.