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Implantable contraceptives have been regarded as effective, but have been plagued by reports of adverse effects and difficulties in removing some types of implant. Some are not now available in the UK because of these problems. In what might be something of a first, a systematic review of clinical studies of a new type of implant - Implanon - has been published before the device is available [1]. Implanon is a single 4 cm by 2 mm flexible rod containing etonorgestrel.


Non-comparative studies of Implanon, and comparative randomised, open studies of Implanon and Norplant in women requiring long-term contraception. The duration was 24 months. Outcomes included pregnancy, ease of insertion and removal of the implant, changes in menstrual bleeding patterns, weight changes and adverse effects.


Two years of data was available from 1333 women using Implanon and 601 using Norplant. No woman became pregnant.

Insertion of Implanon was completed in under three minutes in 90% of women (median one minute), and removed in under five minutes in 83% of women (median two minutes). Norplant, by comparison was inserted in under three minutes in 37% of women (median four minutes) and removed in under five minutes in 36% (median eight minutes).

Bleeding pattern changes were frequent with both implants, and a feature of the data presentation is that percentages of women with particular bleeding abnormalities are given. This provides information that can be used for women to make informed choices about whether the contraceptive method is acceptable to them.

After 24 months of use, 64% of women using Implanon gained at least 1 kg, and 37% gained at least 3 kg. Body mass index increases of more than 10% were found in 20% of women with Implanon and 17% with Norplant.

Discontinuations with Implanon tended to be predominantly in the first year, and 82% of women continued with the device for 24 months (Figure). Reasons for discontinuations were mixed, but were mainly due to bleeding irregularities and a mixture of adverse experiences.

Figure: Percentage of women still using Implanon contraceptive over 24 months of the trials


This form of implanted contraceptive had no method failures in over 70,000 cycles of use, and 82% of women used it for at least two years. Women who withdrew did so mainly because of menstrual irregularity and weight gain. The importance of this paper is that it provides solid information about the consequences of using this method of contraception. There will be no pregnancies, but there are some consequences that some women might prefer to avoid: they should use other methods.

For women who wish absolutely to avoid pregnancy, and who know the risks of bleeding irregularity and weight gain, this might be one of their choices if the device becomes available in the UK.


  1. JE Edwards, A Moore. Implanon: a review of clinical studies. British Journal of Family Planning 1999 4: 3-16.
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