Rios, who passed four of the VADA-administered tests leading up to his match against Pacquiao, failed the urine test afterward. He tested positive for the banned substance methylexanamine, a stimulant that is commonly known as dimenthylamylamine or DMAA and has been used in dietary supplements.
Bob Arum of Top Rank, the promoter for Pacquiao and Rios, confirmed that Rios had failed the post-fight drug test.
“There was a little something in his urine after the fight,’’ Arum said. “It was something they (VADA) reported to the Chinese commission after the fight. He passed all the tests before that. It wasn’t a steroid. It was probably something he took to make weight.’’
Dr. Margret Goodman, the head of VADA, confirmed that Pacquiao passed all five of the tests administered by the organization and that Rios had passed only four of the five.