The contraceptive implant is hormone-based and highly effective, approved in more than 60 countries and used by millions of women around the world. The typical implant is a small flexible tube measuring about 40mm in length and is inserted under the skin by a health care professional. After it is inserted it prevents pregnancy by releasing hormones that prevent ovaries from releasing eggs and thicken cervical mucous. The two most common versions are the single-rod etonogestrel implant and the two-rod levonorgestrel implant. Brands include: Norplant, Jadelle, Implanon, Nexplanon, Sino-implant, Zarin, Femplant and Trust Benefits of the implant include fewer, lighter periods; improved symptoms of premenstrual syndrome; long-lasting, up to three years; smoker- and breastfeeding-safe; and the convenience of not needing to remember to use it every day. In some cases, negative side effects do occur, the most common being irregular bleeding for the first six to 12 months. Less common symptoms include change in appetite, depression, moodiness, hormonal imbalance, sore breasts, weight gain, dizziness, pregnancy symptoms, and lethargy. With regard to helping women space their pregnancies appropriately, there is some debate about the most effective time to insert contraceptive implants after pregnancy. Offering immediate postpartum insertion probably leads to more women initiating use of contraceptive implants, compared to offering insertion at the first postpartum visit, but there may be little or no difference between immediate and delayed insertion in terms of continued use of implants at six months or in terms of women's satisfaction. It is not certain if immediate insertion of implants has any effect on unintended pregnancy or the risk of side effects compared to delayed insertion.
Intrauterine device
An intrauterine device is a small contraceptive device, often 'T'-shaped and containing either copper or the hormonelevonorgestrel, which is implanted into the uterus. They are long-acting, reversible, and the most effective types of reversible birth control. Failure rates with the copper IUD is about 0.8% while the levonorgestrel IUD has a failure rate of 0.2% in the first year of use. Among types of birth control they, along with birth control implants, result in the greatest satisfaction among users. As of 2011, IUDs are the most widely used form of reversible contraception worldwide. IUDs also tend to be one of the most cost-effective methods of contraception for women.
Men
Several barriers exist to expanding research into implantable and other contraceptive methods for men, including vague regulatory guidelines, long device development timelines, men's attitudes towards convenience, and a significant lack of funding. Several implantable devices have been attempted, both hormonal and non-hormonal.
Research
In 2001, Dutch pharmaceutical companyOrganon announced clinical trials of its implantable etonogestrel-based male contraceptive would begin in Europe and the U.S., anticipating a marketable product as early as 2005. Despite promising results, research development stopped, with outside speculation that lack of marketability was a factor. Organon representative Monique Mols stated in 2007 that "espite 20 years of research, the development of a method acceptable to a wide population of men is unlikely." Schering/Bayer had been working on a similar annual implant with quarterly injections but cancelled the research in 2006/2007, declaring that men would most likely view it as "not as convenient as a woman taking a pill once a day." In 2005, a collaboratory project led by the Population Council, the University of California, Los Angeles, and the Medical Research Council began researching a matchstick-sized implant that contains MENT, a "synthetic steroid that resembles testosterone." Clinical trials were set to begin in 2011 or 2012, and the project was ongoing as of 2016, with hopes of gaining approval as the first reversible male contraceptive. In 2006, Shepherd Medical Company received FDA approval for a clinical trial of its non-hormonal implant called an intra vas device, which consists of two plugs that block sperm flow in the vas deferens. Working on the success of its pilot study and solid results from its clinical trials, the company announced it would expand its trials to three U.S. cities later that year. Questions remained about how reversible the procedure would be in the long-term; however, it was expected to be more reversible than a vasectomy. In 2008, the company disbanded due to the economic crisis but has stated it would restart its research with proper funding. In January 2016 news broke of a non-hormonal, implantable valve — the Bimek SLV — with a switch that attaches to the vas deferens, allowing the owner to stop and resume the flow of sperm on demand. A clinical trial of 25 participants was announced to further test the efficacy of the device.
Other animals
Implantable contraception is also an option for animals, particularly for animal managers at zoos and other captive animal facilities who require reversible contraception methods for managing population growth in limited captive habitat. The Association of Zoos and Aquariums' Reproductive Management Center at the Saint Louis Zoo in St. Louis, Missouri has played a major role in researching and disseminating contraception information to hundreds of institutions around the world since 1999 via its Contraception Database, which houses over 30,000 records for hundreds of species. One of the most popular contraceptive methods used by zoos is the melengestrol acetate implant, a progestin-based hormonal contraceptive developed in the mid-1970s. Other progestin-based implants that have been placed in animals include Norplant, Jadelle, and Implanon. Androgen-based implants that use agonistgonadotropin-releasing hormone and, to a lesser degree, IUDs have also seen use in several domestic and exotic species. Whatever the implant, some care must be taken to minimize the risk of implant migration or loss
