Safety and efficacy of Implanon, a single-rod implantable contraceptive containing etonogestrel

Contraception. 2005 May;71(5):319-26. doi: 10.1016/j.contraception.2004.11.007.


Objectives: The safety and efficacy of a single-rod implantable contraceptive containing etonogestrel (Implanontrade mark) were investigated in a multicenter clinical trial.

Study design: Sexually active American women (N=330) with apparently normal menstrual cycles used the implant for up to 2 years. All subjects recorded bleeding and/or spotting daily in a diary. Safety was assessed through adverse experiences (AEs), laboratory tests and physical and gynecologic examinations.

Results: Total exposure was 474 woman-years (6186 cycles), and 68% of subjects had at least 1 year of exposure. No pregnancies occurred. The most common bleeding pattern observed throughout the study was infrequent bleeding, defined as less than three episodes of bleeding in a reference period (excluding amenorrhea). The least common pattern was frequent bleeding, defined as more than five episodes of bleeding in a reference period. Infrequent, prolonged and frequent bleeding patterns were most common early in the study and declined thereafter. During the 3-month Reference Periods 2-8 (Months 4-24), the incidence of amenorrhea ranged from 14% to 20%. Forty-three subjects (13%) withdrew from the study because of bleeding pattern changes and 76 subjects (23%) discontinued because of other AEs. Other common AEs leading to discontinuation, besides bleeding irregularities, were emotional lability (6.1%), weight increase (3.3%), depression (2.4%) and acne (1.5%). Use of Implanon (etonogestrel subdermal implant, referred to herein as ENG implant) for up to 2 years had no clinically significant effects on laboratory parameters, physical and pelvic examinations, vital signs or body mass index. The average length of time required for ENG implant insertion and that for removal were 0.5 and 3.5 min, respectively, and all the procedures were uncomplicated. The return to normal menstrual cycles and fertility was rapid after removal.

Conclusions: Implanon is a safe, highly effective and rapidly reversible new method of contraception.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acne Vulgaris / chemically induced
  • Adolescent
  • Adult
  • Contraceptive Agents, Female / administration & dosage*
  • Contraceptive Agents, Female / adverse effects
  • Desogestrel / administration & dosage*
  • Desogestrel / adverse effects
  • Disposable Equipment
  • Drug Implants*
  • Female
  • Humans
  • Menstrual Cycle / drug effects
  • Progesterone Congeners / administration & dosage*
  • Progesterone Congeners / adverse effects
  • Time Factors
  • United States
  • Uterine Hemorrhage / chemically induced
  • Weight Gain / drug effects


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