Polyestradiol phosphate
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| Clinical data | |
|---|---|
| Trade names | Estradurin |
| AHFS/Drugs.com | International Drug Names |
| Pregnancy category |
|
| Routes of administration |
Intramuscular injection |
| ATC code | L02AA02 (WHO) |
| Legal status | |
| Legal status |
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| Pharmacokinetic data | |
| Protein binding | >95% (estradiol) |
| Metabolism | Mainly liver |
| Biological half-life | 70 days (320 mg i.m.) |
| Excretion | Urine |
| Identifiers | |
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| Synonyms | Leo-114 |
| CAS Number |
28014-46-2 
|
| PubChem (SID) | 51091766 |
| ChemSpider | none |
| UNII |
P14877CDX2
|
| KEGG |
D07434
|
| ChEMBL |
CHEMBL1201477
|
| Chemical and physical data | |
| Formula | (C18H22)m(O4P)n (m, n ≈ 80) |
| Molar mass |
Polymer: ~26 g/mol Repeat unit: 370.382 g/mol |
| Melting point | 195 to 202 °C (383 to 396 °F) |
 (what is this?)
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Polyestradiol phosphate (PEP) (INN, BAN) (brand name Estradurin), also known as estradiol polymer with phosphoric acid or as estradiol 17β-phosphate polymer, is a synthetic, steroidal estrogen and an estrogen ester in the form of a polymer – specifically, the 17β-phosphate ester polymer of estradiol – which is used in the treatment of prostate cancer. It is administered via intramuscular injection once a month and acts as a very long-lasting prodrug of estradiol. PEP was introduced by Pfizer in 1957 and has been marketed in the United States and throughout Europe. It is no longer available in the U.S.
PEP is used as an intramuscular injection for estrogen therapy of prostate cancer. It is available in combination with mepivacaine, a local anaesthetic, to avoid a burning sensation during application. After injection, it releases the active agent estradiol over several weeks.
Intramuscular PEP has been compared to combined androgen blockade (castration + 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, estrogen may have significant advantages relative to ADT in terms of bone loss and fractures, hot flashes, and sexual function, as well as considerable cost savings with parenteral forms of estradiol compared to GnRH analogue therapy. On the other hand, gynecomastia and breast tenderness occur at relatively high rates with estrogens, whereas incidences are low with castration or combined androgen blockade.
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