Estradiol benzoate (EB), sold under the brand name Progynon-B among others, is an estrogen medication which is used in hormone therapy for menopausal symptoms and low estrogen levels in women, in hormone therapy for transgender women, and in the treatment of gynecological disorders. It is also used in the treatment of prostate cancer in men. Estradiol benzoate is used in veterinary medicine as well. When used clinically, the medication is given by injection into muscle usually two to three times per week.

Side effects of estradiol benzoate include breast tenderness, breast enlargement, nausea, headache, and fluid retention. Estradiol benzoate is an estrogen and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol. It is an estrogen ester and a prodrug of estradiol in the body. Because of this, it is considered to be a natural and bioidentical form of estrogen.

Estradiol benzoate was discovered in 1933 and was introduced for medical use that same year. It was the first estradiol ester to be discovered or marketed, and was one of the first estrogens to be used in medicine. Along with estradiol dipropionate, estradiol benzoate was among the most widely used esters of estradiol for many years following its introduction. However, in the 1950s, longer-acting estradiol esters that necessitated less frequent injections, such as estradiol valerate and estradiol cypionate, were developed, and have since largely superseded estradiol benzoate. Nonetheless, estradiol benzoate remains widely available throughout the world. It is not available for medical use in the United States, but is available there for use in veterinary medicine.

The medical uses of estradiol benzoate are the same as those of estradiol and other estrogens. Estradiol benzoate is used in hormone therapy for the treatment of menopausal symptoms such as hot flashes and vaginal atrophy and in the treatment of hypoestrogenism and delayed puberty due to hypogonadism or other causes in women. It is also used in hormone therapy for transgender women. Aside from hormone therapy, estradiol benzoate is used in the treatment of gynecological disorders such as menstrual disorders, dysfunctional uterine bleeding, and breast engorgement. In addition, it is used as a form of high-dose estrogen therapy in the palliative treatment of prostate cancer in men.

Estradiol benzoate has a relatively short duration of action, and is administered by intramuscular injection usually two to three times per week. It is used in the treatment of menopausal symptoms at a dosage of 1 to 1.66 mg initially and 0.33 to 1 mg for maintenance two times per week, and in the treatment of hypoestrogenism and delayed puberty at a dosage of 1.66 mg two to three times per week. The dosage used in hormone therapy for transgender women is 0.5 to 1.5 mg two to three times per week. In the treatment of prostate cancer, estradiol benzoate is used at a dosage of 1.66 mg three times per week (for a total of 5 mg per week).

Estradiol benzoate is and has been available as an oil solution for intramuscular injection provided as vials and ampoules at concentrations of 0.167, 0.2, 0.33, 1, 1.67, 2, 5, 10, 20, and 25 mg/mL. It is also available as a microcrystalline aqueous suspension for intramuscular injection under the brand name Agofollin Depot. Sistocyclin was the brand name of a product containing 10 mg microcrystalline estradiol benzoate and 200 mg microcrystalline progesterone in an aqueous suspension. Follivirin (and previously Femandren M) is the brand name of a product containing 2.5 mg microcrystalline estradiol benzoate and 25 to 50 mg microcrystalline testosterone isobutyrate in aqueous suspension.

A vaginal tablet formulation containing 0.125 mg estradiol benzoate and 10 mg monalazone sodium (a vaginal disinfectant and spermicidal contraceptive) has been marketed under the brand name Malun 25. Estradiol benzoate was also formerly available as 50 and 100 mg pellets for subcutaneous implantation and as a 2 mg/g ointment.

Contraindications of estrogens include coagulation problems, cardiovascular diseases, liver disease, and certain hormone-sensitive cancers such as breast cancer and endometrial cancer, among others.