Chemical castration is castration via drugs, whether to reduce libido and sexual activity, to treat cancer, or otherwise. Unlike surgical castration, where the gonads are removed through an incision in the body, chemical castration does not remove organs, nor is it a form of sterilization. Chemical castration is generally considered reversible when treatment is discontinued, although permanent effects in body chemistry can sometimes be seen, as in the case of bone density loss increasing with length of use of DMPA.
In May of 2016 'nytimes.com' reported that a number of countries use chemical castration on rapists and pedophiles, often in return for reduced sentences.
When used on 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 gynecomastia (development of larger than normal mammary glands in males) as seen in Alan Turing's case.
When used on women, the effects are similar, though there isn't much (if any) research about chemically lowering women's sex drives, since most research focuses on the opposite, but anti-androgenic hormone regimens would lower testosterone in women which can impact sex drive or sexual response. These drugs also deflate the breast glands and expand the size of the nipple. Also seen is a sudden shrink in bone mass and discoloration of the lips, reduced body hair, and muscle mass.
The first use of chemical castration occurred in 1944, when diethylstilbestrol was used with the purpose of lowering men's testosterone. The antipsychotic agent benperidol is sometimes used to diminish sexual urges in people who display inappropriate sexual behavior, and can likewise be given by depot injection. But benperidol does not affect testosterone and is therefore not a castration agent. Chemical castration is often seen as an easier alternative to life imprisonment or the death penalty because it allows the release of sex offenders while reducing or eliminating the chance that they reoffend.