Goserelin

Goserelin is an injectable gonadotropin releasing hormone super-agonist (GnRH agonist). It stops the production of sex hormones (testosterone and oestrogen).

Goserelin is marketed by AstraZeneca with the brand name Zoladex.^[1] It was first launched in 1987 and is currently the second-largest selling GnRH analogue in the world. It is currently available in more than one hundred markets.

Zoladex 3.6 mg subcutaneous monthly biodegradable implant was first approved by the FDA on November 3, 1989^[2] for treatment of prostate cancer, a 10.8 mg subcutaneous 3-month biodegradable implant and other indications were subsequently approved.

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Pharmacokinetics

Goserelin is an GnRH analogue. It is chemically similar to the body's natural GnRH though it has a greatly extended half-life. After administration, peak serum concentrations are reached in about two hours. It rapidly binds to the GnRH 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. 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.^[3]

Indications

  Goserelin is used to treat hormone-sensitive cancers of the prostate and breast (in pre-/perimenopausal women) and some benign gynaecological disorders (endometriosis, uterine fibroids and endometrial thinning). In addition, goserelin is used in assisted reproduction and in the treatment of precocious puberty.

It is available as a 1-month depot and a long-acting 3-month depot. Both depots are used for the treatment of prostate cancer, endometriosis and uterine fibroids but only the 1-month depot is approved for breast cancer, endometrial thinning and assisted reproduction.

Side effects

Goserelin causes an increase in bone pain and symptoms of prostatic cancer during the first few weeks of treatment. As the body adjusts to the medication, the symptoms will disappear. Goserelin may cause hot flushes, headache, stomach upset, difficulty urinating, weight gain, swelling and tenderness of breasts, decreased erections, reduced sexual desire.

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