title: Evaluation of a 1-year levonorgestrel-releasing contraceptive implant: side effects, release rates, and biodegradability.
abstract: OBJECTIVE
  To determine the release rates, effects on ovulation, and side effects of two lengths of a biodegradable, subdermal contraceptive implant containing levonorgestrel in a caprolactone capsule.
  
  
  METHODS
  Phase II randomized clinical trial.
  
  
  METHODS
  Public family planning clinic at an urban general hospital.
  
  
  METHODS
  Forty-eight healthy, parous, ovulating volunteers.
  
  
  METHODS
  Subjects were randomly assigned either a 2.5- or a 4.0-cm contraceptive capsule that was worn under the skin of the upper arm for 1 year if not removed earlier for other reasons.
  
  
  METHODS
  Serum concentrations of levonorgestrel, progesterone, estradiol, and lipoproteins were measured as were metabolic parameters. Vaginal bleeding and other side effects were recorded. After implant removal, remaining levonorgestrel, capsule viscosity, and molecular weight were measured.
  
  
  RESULTS
  The 4-cm implant provided serum concentrations of levonorgestrel ranging from 0.65 ng/mL shortly after insertion to 0.20 ng/mL at 12 months, but the 2.5-cm implant resulted in levels too low for contraception. The 4-cm implant suppressed ovulation in approximately 80% of cycles over 1 year of use, but the 2.5-cm implant failed to suppress ovulation. The implants were rapidly and easily inserted and removed. They retained structural integrity through 1 year of use. Of 48 subjects, 32 had abnormal bleeding patterns; the mean number of days of bleeding per month was 7 with 23 days between episodes. Women using capronor maintained normal metabolic parameters except that low-density lipoprotein decreased slightly.
  
  
  CONCLUSIONS
  The 4.0-cm implant is a promising contraceptive. There were no important metabolic effects, but there were bothersome minor side effects typical of progestin-only contraception.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco.
authors.forename: P D
authors.initials: PD
authors.lastname: Darney
authors.forename: C M
authors.initials: CM
authors.lastname: Klaisle
authors.forename: S E
authors.initials: SE
authors.lastname: Monroe
authors.forename: C E
authors.initials: CE
authors.lastname: Cook
authors.forename: N R
authors.initials: NR
authors.lastname: Phillips
authors.forename: A
authors.initials: A
authors.lastname: Schindler
mesh_terms: D015746:Abdominal Pain / Q000139:chemically induced; D000293:Adolescent; D000328:Adult; D000568:Amenorrhea / Q000139:chemically induced; D003270:Contraceptive Agents / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood; D004341:Drug Evaluation; D004343:Drug Implants; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D007279:Injections, Subcutaneous; D016912:Levonorgestrel / Q000008:administration & dosage* / Q000009:adverse effects / Q000097:blood; D008074:Lipoproteins / Q000097:blood; D010048:Ovarian Cysts / Q000139:chemically induced; D010060:Ovulation / Q000187:drug effects; D011374:Progesterone / Q000097:blood; D013997:Time Factors
chemical_list: D003270:Contraceptive Agents; D004343:Drug Implants; D008074:Lipoproteins; D011374:Progesterone; D004958:Estradiol; D016912:Levonorgestrel