Another performance-enhancing drug that made the 1996 Olympic Games memorable for the wrong reason was bromantan, a sort of stimulant and masking agent combined in one. Several Russians tested positive for the drug, which was not, at the time, included on the International Olympic Committee's (IOC's) list of banned substances. That didn't stop the IOC from disqualifying several Russian athletes, stripping medals from two and, ultimately, blacklisting bromantan based on its performance-enhancing effects.
Those effects are quite unlike any other PED. Russian army doctors developed bromantan as a stimulant, something they could give to soldiers and cosmonauts to help them feel more alert and fight fatigue. Soon after, Russian athletes got hold of the drug, reporting that it helped them perform at peak levels without feeling exhausted. But the story appears more complicated.
Some anti-doping officials believe bromantan can hide the abuse of more serious drugs, such as steroids. This is known as masking, and it's just one more way athletes can find a way to cheat. For example, the masking agent probenecid stops the excretion of steroids for a few hours, decreasing the concentration of steroids in the urine. The exact masking mechanism of bromantan, however, remains unclear. That doesn't diminish the drug's appeal among athletes, who believe its stimulant/masking effects give them a doping double whammy.