NEXPLANON is a radiopaque, progestin-only, soft, flexible implant preloaded in a sterile, disposable applicator for subdermal use. The implant is white/off-white, non-biodegradable and 4 cm in length with a diameter of 2 mm (see Figure 18). Each implant consists of an ethylene vinylacetate (EVA) copolymer core, containing 68 mg of the synthetic progestin etonogestrel and barium sulfate (radiopaque ingredient), surrounded by an EVA copolymer skin. Once inserted subdermally, the release rate is 60-70 meg/day in week 5-6 and decreases to approximately 35-45 meg/day at the end of the first year, to approximately 30-40 meg/day at the end of the second year, and then to approximately 25-30 meg/day at the end of the third year. NEXPLANON is a progestin-only contraceptive and does not contain estrogen. NEXPLANON does not contain latex.

Figure 18 (Not to scale)

Etonogestrel [13-Ethyl-17-hydroxy-11-methylene-18,19-dinor-17a-pregn-4-en-20-yn-3-one], structurally derived from 19-nortestosterone, is the synthetic biologically active metabolite of the synthetic progestin desogestrel. It has a molecular weight of 324.46 and the following structural formula (Figure 19).

Figure 19

Last reviewed on RxList: 6/28/2011
This monograph has been modified to include the generic and brand name in many instances.