Chemical castration is a form of punishment reserved for male sex offenders, typically pedophiles and rapists. It is also a preliminary and concurrent step in hormone treatment for male-to-female transsexualism.
For male sex offenders, chemical castration is more humane than actual castration. Additionally, it is not permanent. For male-to-female transsexuals, the change will be permanent after six months.
Depo-Provera (a progestin) is the drug used today. It "acts on the brain to inhibit hormones that stimulate the testicles to produce testosterone".
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