Here's a very good primer on the single-rod implant, Implanon. You never know; any time now the FDA might just decide to flip a coin and approve it for use in the U.S.
About the size of a matchstick (40 mm long and 2 mm wide), Implanon is a flexible rod that contains ethylene vinyl acetate (EVA) impregnated with 68 mg of etonogestrel (the same drug used in the contraceptive vaginal ring). On average, the rod releases 40 μg of etonogestrel every day, inhibiting ovulation and thickening cervical mucus. The rod is typically inserted in the inside portion of the upper arm during a brief office procedure. High efficacy. Rapid return to fertility. Key [noncontraceptive] advantages of the single-rod implant include no decrease in bone mineral density and no effect on breast milk. But, research on dysmenorrhea [painful period] and acne demonstrate variable effects. For example, a study of 635 women who used Implanon found that 85% of them with dysmenorrhea noted an improvement, while 4% noted new or worsened symptoms. In a study of 231 women with acne at baseline, 16% had less acne, 70% had no change, and 14% had increased acne with the implant. In those without acne at baseline, 16% reported having developed it. The main reason women discontinue the single-rod implant is due to irregular and unpredictable bleeding patterns. During the first 3 months following insertion, up to 40% of women are amenorrheic, 50% have infrequent bleeding (dropping to 30% by 6 months), and 30% have prolonged bleeding (eventually falling to between 10% and 20%). Contraindications: known or suspected pregnancy; active venous thromboembolic [clot] disorder; active or history of severe hepatic [liver] disease; progestogen-dependent tumors; undiagnosed vaginal bleeding; hypersensitivity to implant's components. Also, women with diabetes need to be carefully observed. The average times for insertion and removal are 30 seconds and 3½ minutes, respectively. For women who cannot take estrogen and who desire long-term protection yet rapid reversibility, Implanon may be an attractive choice. But choosing the implant is just one step; being satisfied with the choice and adhering to it is another.