Levonorgestrel Levels in Nonobese and Obese Women Using LNG20, a New Intrauterine Contraceptive [262].

OBJECTIVE: Evaluate the levonorgestrel pharmacokinetics in nonobese and obese women after placement of LNG20 intrauterine contraceptive at 3 years of use.

METHODS: In a clinical trial to evaluate the LNG20 intrauterine contraceptive for contraception, levonorgestrel plasma concentrations were determined in 279 participants at the 36-month visit. Blood samples were collected from 166 nonobese LNG20, 77 obese LNG20, 23 nonobese Mirena, and 13 obese Mirena participants. Levonorgestrel plasma levels between nonobese and obese participants were compared using a Wilcoxon Mann-Whitney test.

RESULTS: The mean plasma levonorgestrel concentrations at month 36 was 135±51 pg/mL for LNG20 overall; 145.8 ±47.7 pg/mL and 111.3±50.4 pg/mL for LNG20 nonobese and obese participants and 132.1±62.6 pg/mL for Mirena overall; 148.5±71.5 pg/mL and 103.2±27.5 pg/mL for Mirena nonobese and obese participants, respectively. Obese participants using LNG20 and Mirena had lower plasma levels than nonobese participants (P<.5). No difference in efficacy in obese and nonobese LNG20 participants was observed for the first 3 years of clinical use.

CONCLUSION: Levonorgestrel plasma concentration at month 36 did not differ between LNG20 and Mirena nonobese and between LNG20 and Mirena obese participants. Obese women demonstrate significantly lower levonorgestrel concentrations than nonobese women in LNG20 with comparable efficacy in both groups, highlighting the predominantly local mechanism of action of the intrauterine contraceptive.