suggest that the implant has a negative effect on pregnancy or a developing fetus. Acne: Acne has been self-reported to be a side effect, and is listed as a side effect by the FDA. However, a study of users found that a majority of users with acne before their insertion reported that their acne had decreased, and only 16% of those who did not have acne before insertion developed acne. Other possible symptoms: Other symptoms that have been reported in trials of implants include headache, emotional lability, abdominal pain, loss of libido, and vaginal dryness. However, there have been no studies that conclusively determine that these symptoms are caused by the implant. Overdose No serious side effects are expected when overdosing contraceptives in general. Interactions Efavirenz, an inducer of the liver enzyme CYP3A4, appears to decrease etonogestrel levels and increase rates of undesired pregnancy among implant users. Similar effects are expected for other CYP3A4 inducers, but it is not known whether these are clinically relevant. The opposite is true of CYP3A4 inhibitors such as ketoconazole, itraconazole and clarithromycin: they might increase etonogestrel concentrations in the body. Device description Nexplanon/Implanon consists of a single rod made of ethylene vinylacetate copolymer that is 4 cm long and 2 mm in diameter. It is similar to a matchstick in size. The rod contains 68 mg of etonogestrel (sometimes called 3-keto-destrogestrel), a type of progestin. Peak serum etonogestrel concentrations have been found to reach 781–894 pg/mL in the first few weeks, gradually decreasing to 192–261 pg/mL after one year, 154–194 pg/mL after two years, and 156–177 pg/mL after three years, maintaining ovulation suppression and contraceptive efficacy. Serum levels maintain relatively stable through 36 months, which implies that the method may be effective for longer than three years. Although not formally approved by the manufacturer for more than three years, studies have shown it remains a highly effective contraceptive for five years. It is a type of progestogen-only contraception. Insertion and removal An experienced clinician must perform the insertion of implants to ensure proper insertion and minimize the risk of nerve damage or misplacement, which could result in pregnancy. Before insertion, the arm is washed with a cleaning solution and a local anesthetic is applied to the upper arm around the insertion area. A needle-like applicator is used to insert the rod under the skin into the subdermal tissue on the inner side of the