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Polyestradiol phosphate
Polyestradiol phosphate (PEP), sold under the brand name Estradurin, is an estrogen medication which is used primarily in the treatment of prostate cancer in men. It is also used in women to treat breast cancer, as a component of hormone therapy to treat low estrogen levels and menopausal symptoms, and as a component of feminizing hormone therapy for transgender women. It is given by injection into muscle once every four weeks.
Common side effects of PEP include headache, breast tenderness, breast development, feminization, sexual dysfunction, infertility, and vaginal bleeding. PEP is an estrogen and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol. It is an estrogen ester in the form of a polymer and is an extremely long-lasting prodrug of estradiol in the body. The biological half-life of PEP is more than two months. Because PEP works by being converted into estradiol, it is considered to be a natural and bioidentical form of estrogen. The safety profile of parenteral estradiol esters like PEP is greatly improved relative to synthetic oral estrogens like ethinylestradiol and diethylstilbestrol.
PEP was discovered around 1953 and was introduced for medical use in the United States in 1957. Along with estradiol undecylate and estradiol valerate, it has been frequently used in the United States and Europe as a parenteral form of estrogen to treat men with prostate cancer. However, it is no longer available in the United States.
PEP is used as an intramuscular injection for estrogen therapy of prostate cancer in men. It is also used to treat breast cancer in women who are at least 5 years postmenopausal. In addition, PEP is used in hormone replacement therapy for low estrogen levels due to hypogonadism or menopause in women. It is also used in feminizing hormone therapy for transgender women. PEP is a form of high-dose estrogen therapy. After an injection, it very slowly releases the active agent estradiol over at least several months.
PEP has been compared to combined androgen blockade (CAB; castration plus flutamide) for the treatment of prostate cancer in a large randomized clinical trial of 915 patients. At 18.5 months, there was no difference in survival or cardiovascular toxicity between the two treatment modalities. These findings suggest that parenteral forms of estradiol may have similar effectiveness and safety relative to androgen deprivation therapy (ADT) in the treatment of prostate cancer. In addition, estrogens may have significant advantages relative to ADT in terms of bone loss and fractures, hot flashes, sexual function, and quality of life, as well as considerable cost savings with parenteral forms of estradiol compared to GnRH analogue therapy. On the other hand, breast tenderness and gynecomastia occur at very high rates with estrogens, whereas incidences are low with castration and CAB. However, gynecomastia with estrogens is generally only mild-to-moderate in severity and is usually only modestly discomforting. In addition, gynecomastia caused by estrogens can be prevented with prophylactic irradiation of the breasts or can be remediated with mastectomy.
PEP has been studied for the treatment of prostate cancer at dosages of 160 mg/month (three studies) and 240 mg/month (four studies). At a dosage of 160 mg/month, PEP incompletely suppresses testosterone levels, failing to reach the castrate range, and is significantly inferior to orchiectomy in slowing disease progression. Conversely, PEP at a dosage of 240 mg/month results in greater testosterone suppression, into the castrate range similarly to orchiectomy, and is equivalent to orchiectomy in effectiveness.
For prostate cancer in men, PEP is usually given at a dosage of 80 to 320 mg every 4 weeks for the first 2 to 3 months to rapidly build up estradiol levels. Thereafter, to maintain estradiol levels, the dosage is adjusted down usually to 40 to 160 mg every 4 weeks based on clinical findings and laboratory parameters. For breast cancer and low estrogen levels in women, the dosage is 40 to 80 mg every 4 weeks. For transgender women, the dosage is 80 to 160 mg every 4 weeks.
PEP is provided in the form of powder or an aqueous solution in vials and ampoules alone or in combination with mepivacaine and/or nicotinamide (vitamin B3) for administration via intramuscular injection. Mepivacaine is a local anaesthetic and is used to avoid a burning sensation during injection of PEP. Each vial/ampoule of Estradurin contains 80 mg PEP, 5 mg mepivacaine hydrochloride, 40 mg nicotinamide, and 2 mL water.
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Polyestradiol phosphate
Polyestradiol phosphate (PEP), sold under the brand name Estradurin, is an estrogen medication which is used primarily in the treatment of prostate cancer in men. It is also used in women to treat breast cancer, as a component of hormone therapy to treat low estrogen levels and menopausal symptoms, and as a component of feminizing hormone therapy for transgender women. It is given by injection into muscle once every four weeks.
Common side effects of PEP include headache, breast tenderness, breast development, feminization, sexual dysfunction, infertility, and vaginal bleeding. PEP is an estrogen and hence is an agonist of the estrogen receptor, the biological target of estrogens like estradiol. It is an estrogen ester in the form of a polymer and is an extremely long-lasting prodrug of estradiol in the body. The biological half-life of PEP is more than two months. Because PEP works by being converted into estradiol, it is considered to be a natural and bioidentical form of estrogen. The safety profile of parenteral estradiol esters like PEP is greatly improved relative to synthetic oral estrogens like ethinylestradiol and diethylstilbestrol.
PEP was discovered around 1953 and was introduced for medical use in the United States in 1957. Along with estradiol undecylate and estradiol valerate, it has been frequently used in the United States and Europe as a parenteral form of estrogen to treat men with prostate cancer. However, it is no longer available in the United States.
PEP is used as an intramuscular injection for estrogen therapy of prostate cancer in men. It is also used to treat breast cancer in women who are at least 5 years postmenopausal. In addition, PEP is used in hormone replacement therapy for low estrogen levels due to hypogonadism or menopause in women. It is also used in feminizing hormone therapy for transgender women. PEP is a form of high-dose estrogen therapy. After an injection, it very slowly releases the active agent estradiol over at least several months.
PEP has been compared to combined androgen blockade (CAB; castration plus flutamide) for the treatment of prostate cancer in a large randomized clinical trial of 915 patients. At 18.5 months, there was no difference in survival or cardiovascular toxicity between the two treatment modalities. These findings suggest that parenteral forms of estradiol may have similar effectiveness and safety relative to androgen deprivation therapy (ADT) in the treatment of prostate cancer. In addition, estrogens may have significant advantages relative to ADT in terms of bone loss and fractures, hot flashes, sexual function, and quality of life, as well as considerable cost savings with parenteral forms of estradiol compared to GnRH analogue therapy. On the other hand, breast tenderness and gynecomastia occur at very high rates with estrogens, whereas incidences are low with castration and CAB. However, gynecomastia with estrogens is generally only mild-to-moderate in severity and is usually only modestly discomforting. In addition, gynecomastia caused by estrogens can be prevented with prophylactic irradiation of the breasts or can be remediated with mastectomy.
PEP has been studied for the treatment of prostate cancer at dosages of 160 mg/month (three studies) and 240 mg/month (four studies). At a dosage of 160 mg/month, PEP incompletely suppresses testosterone levels, failing to reach the castrate range, and is significantly inferior to orchiectomy in slowing disease progression. Conversely, PEP at a dosage of 240 mg/month results in greater testosterone suppression, into the castrate range similarly to orchiectomy, and is equivalent to orchiectomy in effectiveness.
For prostate cancer in men, PEP is usually given at a dosage of 80 to 320 mg every 4 weeks for the first 2 to 3 months to rapidly build up estradiol levels. Thereafter, to maintain estradiol levels, the dosage is adjusted down usually to 40 to 160 mg every 4 weeks based on clinical findings and laboratory parameters. For breast cancer and low estrogen levels in women, the dosage is 40 to 80 mg every 4 weeks. For transgender women, the dosage is 80 to 160 mg every 4 weeks.
PEP is provided in the form of powder or an aqueous solution in vials and ampoules alone or in combination with mepivacaine and/or nicotinamide (vitamin B3) for administration via intramuscular injection. Mepivacaine is a local anaesthetic and is used to avoid a burning sensation during injection of PEP. Each vial/ampoule of Estradurin contains 80 mg PEP, 5 mg mepivacaine hydrochloride, 40 mg nicotinamide, and 2 mL water.