The new version of the contraceptive is called Nexplanon. Like Implanon, it is a progestin-only hormonal birth control delivered through a flexible rod the size of a matchstick. It is inserted under the skin of a woman's upper arm to prevent pregnancy for as long as three years.
This was done, in part, to make removal of the rod easier when it cannot be located manually.
The contraceptive rod still must be implanted by a specially trained health care professional. But a new inserter makes that process much simpler, says ob-gyn Jill Rabin, MD.
Rabin is the head of urogynecology at the Long Island Jewish Medical Center-North Shore LIJ Health System. She has trained other health care professionals to use the new device.
"Instead of four to six steps, the new inserter has two," she tells WebMD. "It is very hard to place it improperly and next to impossible to put in too deeply."
Implanon was first approved for use in the U.S. in 2006, after almost a decade of use in more than 30 other countries.
Effectiveness of Contraceptive Implants
"When implanted correctly, this method is more than 99% effective with less than one pregnancy occurring for every 100 women using it for a year," he says.
The implantable contraceptive prevents pregnancy for up to three years but can be removed at any time, making it a completely reversible, long-acting form of birth control.
Nexplanon prevents pregnancy in three ways: by inhibiting the release of the egg from the ovaries, changing the mucus of the cervix to keep the sperm from reaching the egg, and making it harder for a fertilized egg to implant and develop.
The most common side effect seen with implantable contraception is change in menstrual cycles. Some women have no periods on the birth control, while others have irregular bleeding or heavy bleeding.
A Merck spokesman says the new version of the contraceptive implant is less likely than earlier versions to be inserted improperly or too deeply, which can lead to scarring and nerve damage.