Treatment of endometriosis with a decreasing dosage of a gonadotropin-releasing hormone agonist (nafarelin): a pilot study with low-dose agonist therapy ("draw-back" therapy)

Abstract

Objective: To evaluate the efficacy of half-dose GnRH agonist therapy for endometriosis.

Design: Prospective, longitudinal pilot study.

Setting: Osaka University Hospital.

Patient(s): Patients with symptomatic endometriosis.

Intervention(s): Fifteen patients were randomized to receive either full-dose nafarelin treatment (200 microgram b.i.d.) for 24 weeks (n = 7) or full-dose nafarelin treatment for 4 weeks followed by half-dose nafarelin treatment (200 microgram daily) for 20 weeks (n = 8).

Main outcome measure(s): Clinical symptoms and the results of physical examinations. Serum E(2) and carcinoma antigen 125 (CA125) levels, lipid profiles, and urinary levels of the N-telopeptide of type I collagen. Bone mineral density of the lumbar spine.

Result(s): Subjective and objective manifestations of endometriosis were decreased to a similar extent in both study groups. Adverse effects were markedly reduced with half-dose administration. In the half-dose group, the mean serum E(2) level was significantly suppressed by 4 weeks of treatment with full-dose nafarelin and remained at approximately 30 pg/mL with half-dose nafarelin. Loss of bone mineral density was significantly less with half-dose treatment.

Conclusion(s): Half-dose administration of nafarelin after pituitary down-regulation with full-dose nafarelin ("draw-back" therapy) is a new protocol for the treatment of endometriosis that is effective and associated with fewer adverse effects.