Contraception: hormone implant

What is a hormone implant?

A contraceptive hormone implant is a device that is surgically implanted beneath the skin. Implanon NXT, which is available in Australia, is a small rod 40 mm long and 2 mm thick that is inserted into the upper arm.

How does it work?

Implanon NXT contains etonogestrel, a type of synthetic progesterone, which is steadily released into the bloodstream. It works by stopping the egg from being released from your ovaries (ovulation) and changing the cervical mucus so that sperm can’t penetrate it.

Effectiveness at preventing pregnancy

The effectiveness of a contraceptive method can be measured for perfect use and typical use.

  • Perfect use is when instructions are followed precisely. The failure rate for perfect use of hormone implants during the first year of use is 0.05 to 0.3 per cent. So, when used perfectly, less than one woman in every 100 will become pregnant in the first year.
  • Typical use is what tends to happen in reality. Typical use failures include failures due to incorrect use. The failure rate for hormone implants are 0.05 to 3 per cent in the first year of typical use.


Some of the advantages of contraceptive hormone implants are that they:

  • are a highly effective, long-term form of contraception;
  • allow fertility to return soon after removal;
  • offer immediate protection against pregnancy if inserted in the first 5 days of the menstrual cycle;
  • can be used while breast feeding;
  • do not interfere with intercourse; and
  • can help with painful periods and premenstrual syndrome.


Some of the disadvantages of hormone implants are that they:

  • may cause irregular vaginal bleeding or/and spotting;
  • do not help protect against sexually transmitted infections (STIs);
  • may cause localised bruising or soreness following insertion;
  • may cause a small scar due to the incision made during insertion/removal;
  • cannot be used by women with severe liver disease, breast cancer, unexplained uterine bleeding, or blood clots (deep vein thrombosis); and
  • should not be used by women taking certain medicines (including anti-seizure medicines, certain antibiotics and St John’s wort) that reduce the effectiveness of the implants.

How is it used?

Implanon NXT is inserted under the skin of the upper arm (your left arm if you are right-handed, and vice versa) between the first and fifth day of your menstrual cycle (day one is the first day of bleeding).

The procedure is done under a local anaesthetic using a sterile disposable applicator. You will probably be asked to go back to your doctor after 3 months for a follow-up visit.

The implant must be replaced by your doctor every 3 years.

If you decide at any time that you want to try to get pregnant, the implant can be removed by your doctor and your periods should return quickly.

The implant can usually be removed easily under local anaesthetic. Your doctor will make a small incision (cut) in the skin to remove the implant. A new implant can be inserted at the same site. No stitches are required.

Side effects

Implanon NXT may produce side effects such as:

  • unpredictable bleeding patterns (including prolonged periods, light or no periods);
  • breast tenderness;
  • acne;
  • headaches;
  • mood changes; and
  • weight gain.
Last Reviewed: 9 September 2013


1. Injectable hormonal contraception (revised June 2009). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2013 Jul. (accessed Aug 2013).
2. Family Planning NSW. Contraceptive implant (updated May 2013). (accessed Aug 2013).
3. Family Planning Victoria. Contraceptive implant (Implanon) (updated Jan 2010). (accessed Aug 2013).


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