Add-back therapy: extending safety and efficacy of GnRH analogues in the gynecologic patient.

GnRH analogues have been demonstrated to be effective medical therapy for symptomatic endometriosis. The use of these agents has been limited to 6 months due to hypoestrogenic side effects. A variety of steroidal and nonsteroidal add-back regimens have been used in an effort to eliminate such side effects while maintaining efficacy in order to enhance compliance, safety and duration such side effects while maintaining efficacy in order to enhance compliance, safety and duration of administration of these agents. Only 3 regimens have been shown to be efficacious in prolonging analogue use beyond 6 months by reducing vasomotor symptoms as well as preventing significant bone mineral density loss. These include daily norethindrone acetate 5 mg alone or in conjunction with conjugated equine estrogens 0.625 mg daily, as well as norethindrone 2.5 mg daily in conjunction with an organic bisphosphonate. With further investigation, such regimens may allow safe prolongation of GnRH analogue use without sacrificing efficacy in those endometriosis patients with severe pelvic pain.