Short answer: Goserelin has a half-life of about 4.2 hours (12.1 hours with severe kidney impairment). Levels peak 12 to 15 days in men, 8 to 22 days in women (3.6 mg implant) after a dose. People vary, so treat these as estimates.
Goserelin is a synthetic version of GnRH, the brain hormone that controls LH and FSH. Given continuously, it shuts that signal down and lowers testosterone or estrogen. It is sold as Zoladex, a small implant injected under the skin of the belly every 28 days (3.6 mg) or every 12 weeks (10.8 mg), for prostate cancer, breast cancer and endometriosis.
Also known as: Zoladex.
Zoladex comes as a 3.6 mg implant (every 28 days) and a 10.8 mg implant (every 12 weeks), each preloaded in a single-use syringe and placed under the skin of the front belly wall below the navel, under a physician's supervision. The label says a delay of a few days is allowed, but the schedule should be kept. The 10.8 mg implant is not for women.
The Zoladex 3.6 mg label approves goserelin for prostate cancer (with flutamide before and during radiation for locally confined disease, and for advanced disease), for endometriosis (a 6-month course; retreatment is not recommended because there are no safety data), to thin the uterine lining before endometrial ablation, and for advanced breast cancer in pre- and perimenopausal women. The 10.8 mg implant is approved only for prostate cancer.
The label warns about a short flare of symptoms when treatment starts, high blood sugar and diabetes, a reported higher risk of heart attack, sudden cardiac death and stroke in men on GnRH agonists, high calcium in people with bone metastases, allergic and severe skin reactions, QT prolongation, injection site and blood vessel injury (including serious bleeding), and depression. In women, 6 months of treatment lowered spine bone density by an average of 4.3%. It is not used in pregnancy, except for advanced breast cancer.
WADA bans GnRH agonists, naming goserelin, as testosterone-stimulating peptides in males (S2.2.1), in and out of competition. See also leuprolide and triptorelin.
The Zoladex label gives a half-life of 4.2 hours in people with normal kidneys (measured with a liquid form of goserelin), rising to 12.1 hours with severe kidney impairment. The 3.6 mg implant releases the drug slowly: in its table, levels peaked 12 to 15 days after the implant in men and 8 to 22 days in women. That slow release is why one implant lasts 28 days.
Numbers shown are taken from the source above. Half-life varies from person to person.
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