The original 3.6 mg formulation of Zoladex has been available since 1989 as a monthly implant. The new formation, 10.8 mg goserelin acetate implant given every three months, offers greater convenience to subjects choosing treatment with a luteinizing-hormone-releasing hormone (LHRH) analogue. The 3.6 mg formulation of Zoladex was shown to be as effective as orchiectomy (surgical castration) in controlling the spread of prostate cancer, thus offering men a choice between medical treatment and surgery.
The growth of prostate cancer can be stimulated by the male hormone testosterone. Treatment with Zoladex as a subcutaneous injection results in a decline in testosterone, which then reduces stimulation of hormone-responsive prostate tumors.
The 3-month formulation of Zoladex is a cylindrical implant with a 1.5 mm diameter that contains 10.8 mg of goserelin. Given by subcutaneous injection, the biodegradable implant slowly dissolves, delivering therapeutic levels of the drug continuously over a period of 12 weeks.
In controlled studies of subjects with advanced prostate cancer, the Zoladex 10.8 mg formulation produced pharmacodynamically similar effect in terms of testosterone suppression to that achieved with the 3.6 mg formulation.
The most frequently reported adverse effects in clinical trials with the 10.8 mg formulation were hot flashes and pain.
Zoladex is an analogue of naturally occurring LHRH. Continuous administration of Zoladex results in a significant decline in testosterone production by the testicles. This reduces testosterone stimulation of prostate cancer growth.
The once-a-month Zoladex 3.6 mg formulation was recently cleared by the FDA for the treatment of advanced breast cancer in premenopausal and perimenopausal women. Since 1993, Zoladex has also been used as a treatment for endometriosis, a noncancerous gynecological condition affecting an estimated five million women in the United States.
Prostate cancer is the most common cancer (other than skin cancers) among men in the United States. According to the American Cancer Society, some 244,000 men will be diagnosed with the disease in 1995, and 40,400 men will die of it.