Chemical castration is often done to sex offenders in an effort to prevent future criminal behavior. Per the National Association of Criminal Defense Lawyers, chemical castration involves a weekly injection of Depo-Provera, a contraceptive used by women. This obliterates virtually all testosterone production. The sex offender then as he was prior to puberty. It is recommended that chemical castration be combined with cognitive therapy. There are substantial side effects associated with chemical castration.
One of the side effects that are associated with chemical castration is extreme fatigue. This is due to fluctuating hormones. The fatigue can vary from minor to extreme. Along with fatigue there can be insomnia as well. This creates difficulties as you can feel extremely tired, but be unable to actually sleep.
According to the Legal and Ethical Issues in the Use of Antiandrogens in Treating Sex Offenders, there is often weight gain of 15 to 20 pounds due to chemical castration. This may be due to fatigue or increased appetite. Also, there are hormonal changes that may contribute to weight gain as well.
Impotence is another side effect of chemical castration. It is generally due to the lowered levels of testosterone. As the drugs render a person prepubescent in terms of development and sex drive, it is possible for the drugs to make the individual impotent as well. This is just a possible side effect and not guaranteed.