Etonogestrel contraceptive implant
- Philip D Darney, MD, MSc
Philip D Darney, MD, MSc
- University of California, San Francisco
The etonogestrel implant is a single-rod progestin contraceptive placed subdermally in the inner upper arm for long-acting (three years) reversible contraception in women (figure 1). It was originally marketed under the brand name Implanon, but was subsequently modified and marketed as Nexplanon (figure 2). Implanon and Nexplanon are bioequivalent.
Accumulating evidence supports the safety, efficacy, and acceptability of this contraceptive method [1,2]. From 2011 to 2013, 0.8 percent of women using contraception used an etonogestrel implant, up from 0.3 percent from 2006 to 2010 . Contraception is the only approved indication for the etonogestrel implant, although it has been studied for use in progestin-responsive disorders, such as endometriosis .
This topic will review the etonogestrel contraceptive implant. Information on related contraceptive topics can be found separately. (See "Contraceptive counseling and selection" and "Overview of the use of estrogen-progestin contraceptives" and "Progestin-only pills (POPs) for contraception" and "Intrauterine contraception: Devices, candidates, and selection" and "Contraception: Overview of issues specific to adolescents" and "Postpartum and postabortion contraception".)
STRUCTURE AND PHARMACOKINETICS
The implant consists of a 40 mm by 2 mm semi-rigid plastic (ethylene vinyl acetate) rod containing 68 mg of the progestin etonogestrel (the 3-keto derivative of desogestrel). Etonogestrel is slowly released over at least three years (figure 3), initially at 60 to 70 mcg/day, decreasing to 35 to 45 mcg/day at the end of the first year, to 30 to 40 mcg/day at the end of the second year, and then to 25 to 30 mcg/day at the end of the third year . Data from a prospective study indicate the mean etonogestrel serum concentration is maintained at a level to provide contraception at least through the fifth year of implant use .
Unlike Implanon, the Nexplanon rod is radio-opaque so it can be detected by x-ray and thus does not require magnetic resonance imaging (MRI) for locating an impalpable implant. In addition, the redesigned applicator makes subdermal insertion easier and failed insertion unlikely because the new cap will not open if the implant is not in the needle and a finger pressure activated lever ensures that the trocar completely discharges the contraceptive implant under the skin.
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- Branum AM, Jones J. Trends in long-acting reversible contraception use among U.S. women aged 15-44. NCHS Data Brief 2015; :1.
- Walch K, Unfried G, Huber J, et al. Implanon versus medroxyprogesterone acetate: effects on pain scores in patients with symptomatic endometriosis--a pilot study. Contraception 2009; 79:29.
- Wenzl R, van Beek A, Schnabel P, Huber J. Pharmacokinetics of etonogestrel released from the contraceptive implant Implanon. Contraception 1998; 58:283.
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- Cardiovascular disease and use of oral and injectable progestogen-only contraceptives and combined injectable contraceptives. Results of an international, multicenter, case-control study. World Health Organization Collaborative Study of Cardiovascular Disease and Steroid Hormone Contraception. Contraception 1998; 57:315.
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- STRUCTURE AND PHARMACOKINETICS
- MECHANISM FOR CONTRACEPTION
- General population
- Women at high risk of unintended pregnancy
- Overweight and obese women
- Drug interactions
- SIDE EFFECTS AND ADVERSE EVENTS
- Preinsertion examination and testing
- - Back-up contraception
- Position the patient
- Administer anesthesia
- Verify placement
- Post insertion care and follow-up
- Complications related to insertion
- REMOVAL AND RETURN OF OVULATION
- Difficult removals
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS