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 administered to Russian athletes at the Sochi Winter Olympics consisted of oxandrolone , a metenolone ester, and a trenbolone ester. 
MGA was first synthesized, in 1959, from medroxyprogesterone acetate, which itself had been synthesized the year prior in 1958.  MGA in combination with ethinylestradiol (EE) was introduced in 1963 by British Drug Houses in the United Kingdom under the brand name Volidan (4 mg MGA and 50 μg EE tablets) as an oral contraceptive ,   and this was followed by Serial 28 (1 mg MGA and 100 μg EE tablets) and Volidan 21 (4 mg MGA and 50 μg EE tablets) in 1964 and Nuvacon (2 mg MGA and 100 μg EE tablets) in 1967, all by British Drug Houses also in the .  MGA was approved in 1967 for the treatment of breast cancer.   In the 1970s, it was found to be associated with mammary tumors in beagle dogs, and along with several other progestogens, was withdrawn from several markets as an oral contraceptive.  Subsequent research revealed that there is no similar risk in humans. 
Injectable steroids are injected into muscle tissue, not into the veins. They are slowly released from the muscles into the rest of the body, and may be detectable for months after last use. Injectable steroids can be oil-based or water-based. Injectable anabolic steroids which are oil-based have longer half-life than water-based steroids. Both steroid types have much longer half-lives than oral anabolic steroids. And this is proving to be a drawback for injectables as they have high probability of being detected in drug screening since their clearance times tend to be longer than orals. Athletes resolve this problem by using injectable testosterone early in the cycle then switch to orals when approaching the end of the cycle and drug testing is imminent.