Goserelin

Goserelin acetate (trade name Zoladex, by AstraZeneca) is a drug used to suppress production of the sex hormones (testosterone and estrogen), particularly in the treatment of breast and prostate cancer. It is an injectable gonadotropin releasing hormone superagonist (GnRH agonist), also known as a luteinizing hormone releasing hormone (LHRH) agonist. Structurally, it is a decapeptide.

Goserelin acetate stimulates the production of the sex hormones testosterone and estrogen in a non-pulsatile (non-physiological) manner. This causes the disruption of the endogenous hormonal feedback systems, resulting in the down-regulation of testosterone and estrogen production.

Zoladex was approved by the U.S. Food and Drug Administration in 1989 for treatment of prostate cancer.

Pharmacokinetics

Goserelin is a synthetic analogue of a naturally occurring luteinizing-hormone releasing hormone (LHRH). Bioavailability is almost complete. Goserelin is poorly protein bound and has a serum elimination half-life of two to four hours in patients with normal renal function. The half-life increases with patients with impaired renal function. There is no significant change in pharmacokinetics in subjects with liver failure. After administration, peak serum concentrations are reached in about two hours. It rapidly binds to the LHRH receptor cells in the pituitary gland thus leading to an initial increase in production of luteinizing hormone and thus leading to an initial increase in the production of corresponding sex hormones. This initial flare may be treated by co-prescribing/co-administering an androgen receptor antagonist such as bicalutamide (Casodex). Eventually, after a period of about 14–21 days, production of LH is greatly reduced due to receptor downregulation, and sex hormones are generally reduced to castrate levels.