Chemical castration is the administration of medication designed to reduce libido and sexual activity, usually in the hope of preventing rapists, child molesters and other sex offenders from repeating their crimes. Unlike surgical castration, where the testes are removed through an incision in the scrotum, chemical castration does not actually castrate the person, nor is it a form of sterilization. For this reason the term "chemical castration" has been called a misnomer.
Chemical castration is generally considered reversible when treatment is discontinued; in the case of Depo Provera, "no permanent physical change is wrought in the body. Castration has, from time to time, been used as an instrument of public and/or judicial policy despite concerns over human rights and possible side effects.
Chemical castration involves the administration of anti-androgen drugs, such as cyproterone or the birth-control drug Depo-Provera, which is given as an injection every three months, making compliance easier to track.
When used by men, these drugs can reduce sex drive, compulsive sexual fantasies, and capacity for sexual arousal. Life-threatening side effects are rare, but some users show increases in body fat and reduced bone density, which increase long-term risk of cardiovascular disease and osteoporosis. They may also experience other "feminizing" effects such as gynecomastia , reduced body hair, and loss of muscle mass .