Zoladex

Zoladex is the brand name for goserelin, a synthetic gonadotropin-releasing hormone (GnRH) agonist used to suppress ovarian or testicular hormone production in several conditions. It is delivered as a subcutaneous implant that releases the drug over time. Common formulations include a 3.6 mg implant given monthly and a 10.8 mg implant given every 12 weeks.

Mechanism of action: Goserelin initially stimulates GnRH receptors, causing a transient rise in luteinizing hormone (LH) and follicle-stimulating hormone (FSH). With continuous exposure, the pituitary becomes desensitized and downregulated, leading to suppression of LH and FSH. The result is reduced testosterone in men and reduced estrogen in premenopausal women.

Medical uses: In advanced prostate cancer, Zoladex lowers testosterone to castration levels to slow tumor growth. In premenopausal women, it is used to suppress ovarian function for hormone-sensitive breast cancer and to treat endometriosis or fibroids. It is also used as part of certain fertility procedures to prevent premature ovulation.

Administration and duration: Delivered by subcutaneous implant; dosing intervals depend on the formulation, typically monthly or every three months. Treatment duration varies by condition and response.

Side effects and risks: The most common effects include hot flashes, sweating, reduced libido, mood changes, and injection-site reactions. Long-term use can decrease bone mineral density, increasing osteoporosis risk. Other possible effects include fatigue, headaches, nausea, and sexual dysfunction. Pregnancy is contraindicated during treatment.