Some bodybuilders and athletes use trenbolone esters for their muscle-building and otherwise performance-enhancing effects.  Such use is illegal in the United States and many other countries. The DEA classifies trenbolone and its esters as Schedule III controlled substances under the Controlled Substances Act .  Trenbolone is classified as a Schedule 4 drug in Canada  and a class C drug with no penalty for personal use or possession in the United Kingdom .  Use or possession of steroids without a prescription is a crime in Australia .  The infamous "duchess" cocktail allegedly administered to Russian athletes at the Sochi Winter Olympics consisted of oxandrolone , a metenolone ester, and a trenbolone ester. 
In a study of 1,685 patients treated with CPA, elevated liver enzymes were seen in 10% of patients at a dosage of 50 mg/day and in 20% of patients at a dosage of greater than 100 mg/day.  A study of 2,506 patients given 18–136 mg/day for less than 48 months per patient reported a rate of %.   In a trial of 89 prostate cancer patients who received high-dose CPA for 4 years, there were elevated liver enzymes in % of the patients.  Yet another study of 105 patients found a hepatotoxicity rate of %, with serious hepatic injury occurring in %.  In 2002, it was reported that there were 18 case reports of CPA-associated hepatitis in the medical literature, with 6 of the cases resulting in death.  In addition, a review article cited a report of 96 instances of hepatotoxicity that were attributed to CPA, and 33 of these instances resulted in death.  Moreover, a 2014 review found that 15 cases specifically of CPA-induced fulminant (sudden-onset and severe) liver failure had been reported to date, with only one of these cases not resulting in death.  As such, the prognosis of CPA-induced liver failure is death.