Degarelix (Firmagon)

A hormonal therapy used in the treatment of prostate cancer.

Has an immediate onset of action, binding to gonadotropin-releasing hormone (GnRH) receptors in the pituitary gland and blocking their interaction with GnRH.

This induces a fast and profound reduction in luteinising hormone (LH), follicle-stimulating hormone (FSH) and in turn, testosterone suppression.

Trade name Firmagon

Subcutaneous injection.

Bioavailability is 30-40%, with a protein binding of approximately 90%.

Subject to common peptidic degradation during passage through the hepato-biliary system.

Half-life is 23-61 days.

Excretion approximately 20-30% in the urine, and about 70-80% in the feces.

A synthetic peptide derived of the natural GnRH decapeptide – a hormone that is made by neurons in the hypothalamus.

GnRH antagonists compete with natural GnRH for binding to GnRH receptors in the pituitary gland.

This reversible binding blocks the release of LH and FSH from the pituitary thus leading the suppression of testosterone release.

Unlike the GnRH agonists, which cause an initial stimulation of the hypothalamic-pituitary-gonadal axis, leading to a surge in testosterone levels, and a possible flare-up of the tumor,

GnRH antagonists do not cause an increase in testosterone or clinical flare.

Testosterone surge does not occur with GnRH antagonists, therefore there is no need for patients to receive an antiandrogen as flare protection during prostate cancer treatment.

GnRH agonists also induce an increase in testosterone levels after each injection of the drug, a phenomenon that does not occur with GnRH antagonists.

GnRH antagonists have an immediate onset of action.

GnRH antagonists produce rapid and profound suppression of testosterone and are valuable in the treatment of prostate cancer where fast control of disease is required.

At least as effective as leuprolide at suppressing testosterone to castration levels, and levels are suppressed significantly faster with degarelix than with leuprolide, achieving castration levels by Day 3 of treatment.

Its use may result in longer control of prostate cancer compared with leuprolide.

Commonly associated with side effects such as hot flushes and weight gain.

Because it decreases testosterone to castration levels within three days, it is a useful drug for patients committing sexual child abuse among men.

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