Pharmacokinetics of Implanon. An integrated analysis

Contraception. 1998 Dec;58(6 Suppl):85S-90S. doi: 10.1016/s0010-7824(98)00120-6.


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.

Publication types

  • Meta-Analysis
  • Retracted Publication

MeSH terms

  • Absorption
  • Area Under Curve
  • Biological Availability
  • Body Weight
  • Contraceptive Agents, Female / administration & dosage
  • Contraceptive Agents, Female / blood
  • Contraceptive Agents, Female / pharmacokinetics*
  • Cross-Sectional Studies
  • Desogestrel*
  • Drug Implants
  • Female
  • Humans
  • Infusions, Intravenous
  • Longitudinal Studies
  • Progesterone Congeners / administration & dosage
  • Progesterone Congeners / blood
  • Progesterone Congeners / pharmacokinetics*
  • Radioimmunoassay
  • Vinyl Compounds / administration & dosage
  • Vinyl Compounds / blood
  • Vinyl Compounds / pharmacokinetics*


  • Contraceptive Agents, Female
  • Drug Implants
  • Progesterone Congeners
  • Vinyl Compounds
  • etonogestrel
  • Desogestrel