title: A biodegradable levonorgestrel-releasing implant made of PCL/F68 compound as tested in rats and dogs.
abstract: OBJECTIVE
  Our objective was to report preclinical studies on a biodegradable long-acting contraceptive implant.
  
  
  METHODS
  A poly (epsilon-caprolactone) (PCL)/pluronic F68 (F68) compound was used to construct an implant, which was filled with dry levonorgestrel (LNG) powder (PCL/F68/LNG). LNG release rate, contraceptive efficacy and polymer degradation were evaluated in rats and followed for 2 years. A 2-year toxicity study was conducted in dogs.
  
  
  RESULTS
  The in vitro and in vivo release of LNG from the implant followed zero-order release kinetics. Serum LNG level in rats was very stable during the 2-year period. Studies on polymer degradation indicated that the molecular weight of PCL dropped from 66,000 to 15,000 Da, but the implant was still in good shape by the end of 2 years.
  
  
  CONCLUSIONS
  Toxicological study demonstrated that the PCL/F68 polymer had no adverse effect in all aspects. The contraceptive efficacy in rats showed dose response. The implant was physically and chemically stable for up to 3 years in airproof aluminum foil packing at room temperature.
authors.affiliation: The Tianjin Key Laboratory of Biomaterials, Institute of Biomedical Engineering, Peking Union Medical College and Chinese Academy of Medical Sciences, Nankai District, Tianjin 300192, China.
authors.forename: Guilei
authors.initials: G
authors.lastname: Ma
authors.forename: Cunxian
authors.initials: C
authors.lastname: Song
authors.forename: Hongfan
authors.initials: H
authors.lastname: Sun
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Xigang
authors.initials: X
authors.lastname: Leng
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D003271:Contraceptive Agents, Female / Q000008:administration & dosage*; D004285:Dogs; D004343:Drug Implants / Q000737:chemistry; D005260:Female; D007700:Kinetics; D016912:Levonorgestrel / Q000008:administration & dosage* / Q000493:pharmacokinetics; D008297:Male; D008970:Molecular Weight; D020442:Poloxamer / Q000737:chemistry / Q000633:toxicity; D011091:Polyesters / Q000737:chemistry / Q000633:toxicity; D011108:Polymers / Q000737:chemistry; D051381:Rats; D017208:Rats, Wistar
chemical_list: D003271:Contraceptive Agents, Female; D004343:Drug Implants; D011091:Polyesters; D011108:Polymers; D020442:Poloxamer; C016240:polycaprolactone; D016912:Levonorgestrel