CKS is no longer commissioned by the National Institute for Health and Clinical Excellence (NICE). NICE remains committed to providing a replacement service for CKS and is currently reviewing its options. In the meantime, although CKS content is now not being maintained, it still remains relevant and will continue to be made available. CKS content was generated under a programme of topic creation and update. To check if the topic you are viewing is current or out of date, please refer to the topic publication details by clicking on the 'How up-to-date is this topic?' link in the left hand menu on individual topic pages.
Contraception - Background information
How do progestogen-only implants prevent pregnancy?
- The progestogen-only implant, Implanon®, prevents pregnancy by inhibiting ovulation. It also causes changes in cervical mucus that inhibit sperm.
- Implanon® contains 68 mg of etonogestrel dispersed in a membrane of ethylene vinyl acetate. When inserted under the skin of the inner upper arm it delivers etonogestrel at a dose sufficient to suppress ovulation in 95% of cycles for 3 years of use [Makarainen et al, 1998].
- Serum etonogestrel concentrations rise rapidly after insertion of the implant, and ovulation is likely to be inhibited within 24 hours.
[National Collaborating Centre for Women's and Children's Health, 2005; ABPI Medicines Compendium, 2006]
© NHS Institute for Innovation and Improvement