RETRACTED: Pharmacokinetics of Implanon. An integrated analysis.
The aims of this paper were to present data on the pharmacokinetics, clearance, bioavailability, and in vivo absorption of etonogestrel (ENG); to present the results of a longitudinal analysis of the plasma concentration-time curves of ENG; and to present the results of a cross-sectional analysis on the association of body weight with serum ENG concentrations. Implanon had an absorption rate of almost 60 micrograms/day after 3 months, which slowly decreased to 30 micrograms/day at the end of 2 years. The bioavailability over this period of time was constant and close to 100%. The clearance remained around 7.5 L/h. With a bioavailability and clearance that remained constant, it was concluded that accumulation of ENG does not occur. After Implanon insertion, serum concentrations increased within 8 h to concentrations associated with ovulation inhibition. Maximum mean serum concentrations (Cmax) amounted to 813 pg/mL and the time (tmax) to reach Cmax was 4 days. After reaching Cmax, ENG serum concentrations declined to about 196 pg/mL at the end of the first year, followed by a slow decline to 156 pg/mL at the end of the third year. After removal of Implanon, serum ENG concentrations declined to levels less than the detection limit of the assay (20 pg/mL) within 1 week. Lower body weight was associated with higher serum ENG concentrations.
Huber
J
J
University of Vienna, General Hospital, Department of Obstetrics and Gynecology, Austria.
Wenzl
R
R
D000042:Absorption; D019540:Area Under Curve; D001682:Biological Availability; D001835:Body Weight; D003271:Contraceptive Agents, Female / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D003430:Cross-Sectional Studies; D017135:Desogestrel; D004343:Drug Implants; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008137:Longitudinal Studies; D045167:Progesterone Congeners / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D011863:Radioimmunoassay; D014753:Vinyl Compounds / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D003271:Contraceptive Agents, Female; D004343:Drug Implants; D045167:Progesterone Congeners; D014753:Vinyl Compounds; C044815:etonogestrel; D017135:Desogestrel