Goserelin Acetate Implant: A Depot Luteinizing Hormone-Releasing Hormone Analog for Advanced Prostate Cancer

Goserelin acetate implant is a newly approved depot formulation of a luteinizing hormone-releasing hormone (LHRH) agonist indicated for palliation of advanced prostate cancer. LHRH superagonists suppress gonadotropin release from the pituitary gland by causing down-regulation of receptors. The sustained-release dosage form contains goserelin acetate dispersed in a biodegradable copolymer matrix and is designed to release active drug over 28 days. Pharmacokinetic studies have demonstrated that, despite nonzero order release of goserelin from the matrix, goserelin acetate implant maintains serum concentrations of testosterone in the range normally found in castrated men (<2 nmol/L) throughout the recommended 28-day dosing interval. Response rates similar to those for orchiectomy and estrogen administration have been demonstrated. Combination therapy with either diethylstilbestrol or flutamide has produced favorable results, although the major advantage appears to be a reduction in the tumor flare seen during the first week of LHRH agonist therapy rather than an increase in response rate or survival. Adverse effects are similar to other LHRH agonists and include tumor flare during the first week of therapy, decreased libido, decreased erectile potency, hot flashes, and gynecomastia. In combination with flutamide, additional adverse effects include diarrhea, nausea, vomiting, and elevated hepatic aminotransferases, all of which can be attributed to flutamide administration. Local reactions are minimal; however, some patients require a local anesthetic before goserelin acetate implant injection. The recommended dose is 3.6 mg administered subcutaneously into the upper abdominal wall every 28 days. The average wholesale cost is approximately $320 per month. Formulary addition is recommended.