# Quinestrol

Quinestrol, also known as ethinylestradiol cyclopentyl ether (EECPE), sold under the brand name Estrovis among others, is an estrogen medication which has been used in menopausal hormone therapy, hormonal birth control, and to treat breast cancer and prostate cancer. It is taken once per week to once per month by mouth.

## Medical uses

Quinestrol has been used as the estrogen component in menopausal hormone therapy and in combined hormonal birth control. It has also occasionally been used in the treatment of breast cancer and prostate cancer, as well as to suppress lactation. On its own as an estrogen, quinestrol was taken once per week by mouth. As a combined birth control pill, it was used together with quingestanol acetate and was taken once per month by mouth.

## Pharmacology

Quinestrol is a prodrug of ethinylestradiol (EE), with no estrogenic activity of its own. It is taken orally and has prolonged activity following a single dose, with a very long biological half-life of more than 120 hours (5 days) due to enhanced lipophilicity and storage in fat. Because of its much longer half-life, quinestrol is two to three times as potent as EE. Also because of its long half-life, quinestrol can be taken once a week or once a month.
Following administration, quinestrol is absorbed via the lymphatic system, is stored in adipose tissue, and is gradually released from adipose tissue.
vte Affinities and estrogenic potencies of estrogen esters and ethers at the estrogen receptors :
| Estrogen | Other names | RBATooltip Relative binding affinity (%)$^a$ | REP (%)$^b$ | REP (%)$^b$ |
| Estrogen | Other names | ER | ERα | ERβ |
| Estradiol | E2 | 100 | 100 | 100 |
| Estradiol 3-sulfate | E2S; E2-3S | ? | 0.02 | 0.04 |
| Estradiol 3-glucuronide | E2-3G | ? | 0.02 | 0.09 |
| Estradiol 17β-glucuronide | E2-17G | ? | 0.002 | 0.0002 |
| Estradiol benzoate | EB; Estradiol 3-benzoate | 10 | 1.1 | 0.52 |
| Estradiol 17β-acetate | E2-17A | 31–45 | 24 | ? |
| Estradiol diacetate | EDA; Estradiol 3,17β-diacetate | ? | 0.79 | ? |
| Estradiol propionate | EP; Estradiol 17β-propionate | 19–26 | 2.6 | ? |
| Estradiol valerate | EV; Estradiol 17β-valerate | 2–11 | 0.04–21 | ? |
| Estradiol cypionate | EC; Estradiol 17β-cypionate | ?$^c$ | 4.0 | ? |
| Estradiol palmitate | Estradiol 17β-palmitate | 0 | ? | ? |
| Estradiol stearate | Estradiol 17β-stearate | 0 | ? | ? |
| Estrone | E1; 17-Ketoestradiol | 11 | 5.3–38 | 14 |
| Estrone sulfate | E1S; Estrone 3-sulfate | 2 | 0.004 | 0.002 |
| Estrone glucuronide | E1G; Estrone 3-glucuronide | ? | <0.001 | 0.0006 |
| Ethinylestradiol | EE; 17α-Ethynylestradiol | 100 | 17–150 | 129 |
| Mestranol | EE 3-methyl ether | 1 | 1.3–8.2 | 0.16 |
| Quinestrol | EE 3-cyclopentyl ether | ? | 0.37 | ? |
| Footnotes: $^a$ = Relative binding affinities (RBAs) were determined via in-vitro displacement of labeled estradiol from estrogen receptors (ERs) generally of rodent uterine cytosol. Estrogen esters are variably hydrolyzed into estrogens in these systems (shorter ester chain length -> greater rate of hydrolysis) and the ER RBAs of the esters decrease strongly when hydrolysis is prevented. $^b$ = Relative estrogenic potencies (REPs) were calculated from half-maximal effective concentrations (EC$_{50}$) that were determined via in-vitro β‐galactosidase (β-gal) and green fluorescent protein (GFP) production assays in yeast expressing human ERα and human ERβ. Both mammalian cells and yeast have the capacity to hydrolyze estrogen esters. $^c$ = The affinities of estradiol cypionate for the ERs are similar to those of estradiol valerate and estradiol benzoate (figure). Sources: See template page. |||||
vte Potencies of oral estrogens :
| Compound | Dosage for specific uses (mg usually) | Dosage for specific uses (mg usually) | Dosage for specific uses (mg usually) | Dosage for specific uses (mg usually) | Dosage for specific uses (mg usually) | Dosage for specific uses (mg usually) |
| Compound | ETD | EPD | MSD | MSD | OID | TSD |
| Estradiol (non-micronized) | 30 | ≥120–300 | 120 | 6 | - | - |
| Estradiol (micronized) | 6–12 | 60–80 | 14–42 | 1–2 | >5 | >8 |
| Estradiol valerate | 6–12 | 60–80 | 14–42 | 1–2 | - | >8 |
| Estradiol benzoate | - | 60–140 | - | - | - | - |
| Estriol | ≥20 | 120–150 | 28–126 | 1–6 | >5 | - |
| Estriol succinate | - | 140–150 | 28–126 | 2–6 | - | - |
| Estrone sulfate | 12 | 60 | 42 | 2 | - | - |
| Conjugated estrogens | 5–12 | 60–80 | 8.4–25 | 0.625–1.25 | >3.75 | 7.5 |
| Ethinylestradiol | 200 μg | 1–2 | 280 μg | 20–40 μg | 100 μg | 100 μg |
| Mestranol | 300 μg | 1.5–3.0 | 300–600 μg | 25–30 μg | >80 μg | - |
| Quinestrol | 300 μg | 2–4 | 500 μg | 25–50 μg | - | - |
| Methylestradiol | - | 2 | - | - | - | - |
| Diethylstilbestrol | 2.5 | 20–30 | 11 | 0.5–2.0 | >5 | 3 |
| DES dipropionate | - | 15–30 | - | - | - | - |
| Dienestrol | 5 | 30–40 | 42 | 0.5–4.0 | - | - |
| Dienestrol diacetate | 3–5 | 30–60 | - | - | - | - |
| Hexestrol | - | 70–110 | - | - | - | - |
| Chlorotrianisene | - | >100 | - | - | >48 | - |
| Methallenestril | - | 400 | - | - | - | - |
| Sources and footnotes: ↑ ↑ Dosages are given in milligrams unless otherwise noted. 1 2 3 Dosed every 2 to 3 weeks 1 2 3 Dosed daily 1 2 In divided doses, 3x/day; irregular and atypical proliferation. |||||||

## Chemistry

Quinestrol, also known as ethinylestradiol 3-cyclopentyl ether (EE2CPE), is a synthetic estrane steroid and a derivative of estradiol. It is an estrogen ether, specifically the C3 cyclopentyl ether of ethinylestradiol (17α-ethynylestradiol). Closely related estrogens include mestranol (ethinylestradiol 3-methyl ether) and ethinylestradiol sulfonate (EES; Turisteron; ethinylestradiol 3-isopropylsulfonate).

## History

Quinestrol was developed and introduced for medical use in the 1960s.

## Society and culture
### Generic names

Quinestrol is the generic name of the drug and its INNTooltip International Nonproprietary Name, USANTooltip United States Adopted Name, and BANTooltip British Approved Name. It is also known by its former developmental code name W-3566.

### Brand names

Quinestrol has been marketed under brand names including Agalacto-Quilea, Basaquines, Eston, Estrovis, Estrovister, Plestrovis, Qui-Lea, Soluna, and Yueketing, among others.

### Availability

Quinestrol was marketed as Estrovis in the United States by Parke-Davis and as Qui-Lea in Argentina, but is reportedly not currently marketed. However, it does appear to still be available as an oral contraceptive in combination with progestins in Argentina and China.
One tablet form available in China consists of 6 mg levonorgestrel and 3 mg quinestrol; it is used as a prescription "long-term" oral contraceptive, with one dose taken each month. It is sold under various brand names including Yuèkětíng (Chinese: 悦可婷) and Àiyuè (Chinese: 艾悦). A version with the racemic norgestrel in place of levonorgestrel also appears to be available.

## Veterinary use
### Rodents

The Chinese levonorgestrel/quinestrol 2:1 formula is known as EP-1 in veterinary practice. It is known to have some organ-specific effects on the Mongolian gerbil as measured by receptor mRNA expression. Incorporated into baits at a concentration of 50 ppm, EP-1 has been used to control wild Mongolian gerbil populations with some success.