Intra-vas deferens injection of styrene maleic anhydride gel for male contraception: is it safe?

Implanon® consists of a core and a membrane. The core contains 68 mg etonogestrel dispersed in a matrix of ethylenevinylacetate (EVA) co-polymer and the external membrane is made of EVA co-polymer (0.06 mm).2 This differs from the Norplant subdermal contraceptive device in which the levonorgestrel powder is free within the silastic cavity, and if this cavity is broken the powder will be dispersed. The specific design of Implanon® ensures a controlled release of etonogestrel over 3 years. It is not possible to say that the prolonged heavy bleeding experienced by the patient described in this case report was due to the broken implant. In fact, 10–20% of women using Implanon® will have prolonged bleeding at some point.1 In addition, there were other possible causes, including the fact that the patient had lost a lot of weight and suffered severe stress during this time. However, it remains a possibility that because of the disruption of the specially designed, controlled release mechanism, varying amounts of etonogestrel were being released which may have been responsible for the prolonged bleeding in this patient. When the implant was replaced with a new device the bleeding settled. Another concern would be that the effectiveness of Implanon® as a contraceptive could be diminished if the rate-releasing mechanism is disrupted, although there is no evidence for this. This case report is important in that it is the first to demonstrate that an Implanon® device can be fractured in situ. The clinical significance of this is unknown, but it if a fractured device is suspected then we would recommend that it be replaced.