• Assessment of x-ray visibility by x-ray imaging. [ Time Frame: Just after rod insertion (<= 14 days), and just before rod removal (<= 14 days). ] [ Designated as safety issue: No ]
• Contraceptive efficacy as determined by urine pregnancy test. [ Time Frame: At screening, just before implant insertion, at all visits from month 2 onwards, and at 36 months (or at time of implant removal if discontinuing early). ] [ Designated as safety issue: No ]
• Drug safety as determined by [S]AE monitoring, physical and gynecological history/exams, vital signs, and inspection of implantation site. [ Time Frame: [S]AEs reported whenever they occur. Phys/gyn history/exams, and vital signs done at screening. Vital signs also done at each study visit (2 mos. onwards). Phys/gyn exams at 36 months. Inspection of implant site at 2 months and all subsequent visits. ] [ Designated as safety issue: Yes ]

The primary purpose of this study is to demonstrate the bioequivalence of IMPLANON and Radiopaque IMPLANON. As a secondary objective, the x-ray visibility of Radiopaque IMPLANON will be assessed.

• Drug: Radiopaque Implanon
• Drug: Implanon (etonogestrel implant)

• Active Comparator: Radiopaque Implanon
• Active Comparator: Implanon (etonogestrel implant)

Inclusion Criteria:

• At least 18 but not older than 40 years of age at the time of screening
• Good physical and mental health
• Regular cycles with a usual length between 24 and 35 days
• Body mass index = 18 and = 29
• Willing to give informed consent in writing

Exclusion Criteria:

• Contraindications:

  • known or suspected pregnancy
  • active venous thromboembolic disorder (e.g. deep vein thrombosis,pulmonary embolism)
  • presence or history of severe hepatic disease as long as liver function values have not returned to normal
  • malignancy or pre-malignancy, if sex -steroid-influenced
  • undiagnosed vaginal bleeding
  • hypersensitivity to any of the components of Implanon/Radiopaque Implanon
• Hypertension, i.e. systolic blood pressure >140 mmHg and/or diastolic blood pressure > 90 mmHg.
• A history during pregnancy or during previous use of sex steroids of: jaundice and/or severe pruritus related to cholestasis; gallstone formation; porphyria; systemic lupus erythematosus; haemolytic uraemic syndrome; Sydenham's chorea; herpes gestationis; otosclerosis-related hearing loss
• Present use or use during 2 months prior to the start of Implanon/Radiopaque Implanon of one of the following drugs: phenytoin, phenobarbital, primidone, carbamazepine, rifampicin, oxcarbazepine, topiramate, felbamate, ritonavir, nelfinavir, griseofulvin or the herbal remedy St John's wort.
• Administration of investigational drugs within 2 months prior to the start of Implanon/Radiopaque Implanon