Implanon failure or a natural event?

©FFPRHC J Fam Plann Reprod Health Care 2007: 33(2) Case report I would like to present the case of a 38-year-old woman who suffered an ectopic pregnancy whilst using Implanon® (Organon Laboratories Ltd, Cambridge, UK), the etonogestrel contraceptive implant, for contraception. Of interest, the patient reported an unplanned pregnancy 15 years ago following a true method failure of the combined oral contraceptive pill. The patient gave birth and delivered a healthy child. She then had a miscarriage and, following a condom accident, a further unplanned pregnancy that resulted in an abortion in April 2003. Having had two unplanned pregnancies following contraceptive failures, the patient decided to use Implanon, the progestogen-only contraceptive implant. This was inserted on 5 August 2003. It is interesting to note that this patient had regular menstrual cycles whilst using Implanon, suggesting that she was ovulating regularly. Unfortunately, she contacted the Contraception and Sexual Health Clinic on 8 March 2006 following a laparoscopic salpingectomy for a left-sided ectopic pregnancy performed on 2 March 2006. Therefore this pregnancy had occurred after using Implanon for 2 years and 7 months. When the patient was reviewed she stated that she had not taken any liver enzyme-inducing drugs or herbal remedies. Her body mass index was 26 kg/m2. The contraceptive implant was easily palpable on the medial aspect of her upper left arm. After discussion with Organon Laboratories blood was taken for a serum etonogestrel assay. The patient was also counselled about her future contraceptive needs. She decided to use Depo-Provera® (Pfizer Ltd, Tadworth, UK), the progestogen-only injectable. A week later the patient returned to the clinic to have the implant removed and this was again sent for analysis. The serum etonogestrel assay showed a quantitative level of 46.8 pg/ml. The lower level of quantification is 30 pg/ml and the minimal level needed to inhibit ovulation is 90 pg/ml. Studies have shown that after 2 years of Implanon use a mean serum etonogestrel concentration of 190 ± 43 pg/ml is to be expected. Organon Laboratories’ manufacturing technology department inspected the implant. The measured ex vivo release rate of 43.9 μg/day was well above the declared minimum release rate of approximately 21 μg/day expected for the in situ period of 951 days. Moreover, the residual content of etonogestrel in the implant (and hence the in vivo release amount) was within the expected range.