Serum and peritoneal fluid levels of levonorgestrel in women with endometriosis who were treated with an intrauterine contraceptive device containing levonorgestrel

OBJECTIVE: To determine and compare levels of levonorgestrel (Lng) in serum and peritoneal fluid (PF) of patients on the Lng intrauterine system Mirena (Schering Health, Berlin, Germany) for endometriosis and to relate these to symptoms. DESIGN: Prospective clinical trial. SETTING: Gynecology unit of a teaching hospital. PATIENT(S): Women with minimal to moderate endometriosis at diagnostic laparoscopy. INTERVENTION(S): Mirena was inserted at diagnostic laparoscopy and blood and PF collected for Lng levels. Levonorgestrel was again quantified in serum at 1, 3, and 6 months and PF at 6 months. MAIN OUTCOME MEASURE(S): Serum and PF Lng levels during 6 months, differences in levels before and 6 months after Mirena insertion, and the relationship between these levels and symptoms of endometriosis. RESULT(S): There was significant improvement in symptoms after 6 months on Mirena. The mean (SD) serum Lng levels were 459.2 (100.2), 368.2 (51.8), and 357.3 (53.0) pg/mL at 1, 3, and 6 months, respectively. The PF levels at 6 months were approximately two-thirds the serum levels in patients showing improvement in symptoms. CONCLUSION(S): Mirena delivers significant amounts of Lng into the PF and serum. The relationship between Lng levels in these compartments is linear.