title: Levonorgestrel release rates over 5 years with the Liletta® 52-mg intrauterine system.
abstract: To understand the potential duration of action for Liletta®, we conducted this study to estimate levonorgestrel (LNG) release rates over approximately 5½years of product use.
  
  
  
  Clinical sites in the U.S. Phase 3 study of Liletta collected the LNG intrauterine systems (IUSs) from women who discontinued the study. We randomly selected samples within 90-day intervals after discontinuation of IUS use through 900days (approximately 2.5years) and 180-day intervals for the remaining duration through 5.4years (1980days) to evaluate residual LNG content. We also performed an initial LNG content analysis using 10 randomly selected samples from a single lot. We calculated the average ex vivo release rate using the residual LNG content over the duration of the analysis.
  
  
  
  We analyzed 64 samples within 90-day intervals (range 6-10 samples per interval) through 900days and 36 samples within 180-day intervals (6 samples per interval) for the remaining duration. The initial content analysis averaged 52.0±1.8mg. We calculated an average initial release rate of 19.5mcg/day that decreased to 17.0, 14.8, 12.9, 11.3 and 9.8mcg/day after 1, 2, 3, 4 and 5years, respectively. The 5-year average release rate is 14.7mcg/day.
  
  
  
  The estimated initial LNG release rate and gradual decay of the estimated release rate are consistent with the target design and function of the product. The calculated LNG content and release rate curves support the continued evaluation of Liletta as a contraceptive for 5 or more years of use.
  
  
  
  Liletta LNG content and release rates are comparable to published data for another LNG 52-mg IUS. The release rate at 5years is more than double the published release rate at 3years with an LNG 13.5-mg IUS, suggesting continued efficacy of Liletta beyond 5years.
authors.affiliation: Department of Department of Obstetrics and Gynecology, University of California, Davis, Sacramento, CA, USA. Electronic address: mdcreinin@ucdavis.edu.
authors.forename: Mitchell D
authors.initials: MD
authors.lastname: Creinin
authors.affiliation: Medicines360, San Francisco, CA, USA.
authors.forename: Rolf
authors.initials: R
authors.lastname: Jansen
authors.affiliation: Medicines360, San Francisco, CA, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Starr
authors.affiliation: University of Maryland School of Pharmacy, Baltimore, MD, USA.
authors.forename: Joga
authors.initials: J
authors.lastname: Gobburu
authors.affiliation: University of Maryland School of Pharmacy, Baltimore, MD, USA.
authors.forename: Mathangi
authors.initials: M
authors.lastname: Gopalakrishnan
authors.affiliation: Medicines360, San Francisco, CA, USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: Olariu
mesh_terms: D000293:Adolescent; D000328:Adult; D003271:Contraceptive Agents, Female / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations / Q000493:pharmacokinetics; D005260:Female; D006801:Humans; D007436:Intrauterine Devices, Medicated; D016912:Levonorgestrel / Q000493:pharmacokinetics*; D008875:Middle Aged; D013997:Time Factors; D055815:Young Adult
chemical_list: D003271:Contraceptive Agents, Female; D003692:Delayed-Action Preparations; D016912:Levonorgestrel
keywords: Contraception; Intrauterine device; Levonorgestrel; Liletta; Release rate