The patient presented in case 1 experienced Implanon® failure within 29 months of placement. The pregnancy was uncomplicated and resulted in the delivery of a viable male infant at term, with no apparent anomalies or significant harm from Implanon®. In this particular case, product failure is most likely to blame. All other causes of failure, including failure to insert the product and expulsion were excluded. The patient was not simultaneously using other medications, including ones that induce hepatic enzymes, and had no pre-existing medical condition. Seeing as that the Implanon® had been in place for a total of 29 months, one could potentially argue that the efficacy of the device had decreased as the duration of implant use approached …show more content…
Transvaginal ultrasound revealed an abnormal gestational sac and the pregnancy ultimately resulted in a complete spontaneous abortion. This patient was concurrently using the anti-epileptic agent Carbamazepine for her history of epilepsy. After reviewing the literature, another case report of a patient with epilepsy on Carbamazepine who became pregnant 18 months after Implanon® insertion was cited within a study by Gaffield et al [7]. Failure of hormonal contraceptives secondary to hepatic enzyme-inducing medications results from the mechanism in which sex steroids are metabolized by the liver. Sex steroids are transported into the portal system where they are metabolized to inactive compounds by cytochrome P450 (CYP450) enzymes. Many of the anti-epileptic agents used today, including Carbamazepine, induce the CYP450 enzymes within the liver and thus accelerate the metabolism of hormonal contraceptives, decreasing their duration of action. Carbamazepine also increases the levels of serum sex hormone-binding globulin (SHBG), leading to increased binding of sex hormones (such as etonogestrel), thereby decreasing the concentration of free contraceptive hormone present in the serum