Etonogestrel contraceptive implant, sold under the brandnames Nexplanon and Implanon, is a single-rod subdermal contraceptive implant made by Merck & Co. that is inserted just under the skin of a woman's upper arm and contains etonogestrel. Nexplanon/Implanon are a type of long-acting reversible contraception, the most effective form of birth control. Nexplanon and Implanon NXT are essentially identical to Implanon except Nexplanon and Implanon NXT have 15 mg of barium sulphate added to the core, so it is detectable by x-ray. Nexplanon / Implanon NXT also has a pre-loaded applicator for easier insertion. Implanon was first approved for use in Indonesia in 1998, then approved for use in the United States in 2006. Subdermal contraceptive implants are now used by 11 million women around the world and approved for use in over 60 countries as of 2003.