Joan Guzman, who knocked out Jason Davis in December and then tested positive for the diuretic Furosemide, admitted he used the banned substance at a hearing before the Nevada State Athletic Commission and was fined and suspended, according to executive director Keith Kizer.
Guzman, a former junior featherweight and junior lightweight titleholder, was fined $3,750 -- 25 percent of his $15,000 purse -- and suspended for eight months from the date of the fight. The result of the welterweight bout, which Guzman initially won via second-round knockout, was changed to a no contest.
The 34-year-old Guzman, who has been released from his promotional contract by Golden Boy, fought Davis on Dec. 11 at Mandalay Bay in Las Vegas on the untelevised undercard of junior welterweight titlist Amir Khan's defense against Marcos Maidana.
At the weigh-in the day before the fight, Guzman scaled 144 pounds for a fight that had been contracted at 141.
Kizer said Guzman admitted to the commission at the hearing last week that he took the banned substance to lose weight and "purposefully" did not mention it on his pre-fight medical questionnaire and did not tell anyone in his camp he was taking it.
Guzman has had a history of trouble making weight for his fights. Diuretics are often used to assist with weight loss.
This was the second fight in a row, and at least the third time in his career, that Guzman failed to make the contract weight.
Last March, Guzman, of the Dominican Republic but living in New York, was supposed to weigh a maximum of 135 to challenge Ali Funeka for a vacant lightweight belt. Instead, he showed up a whopping nine pounds overweight. The fight went on anyway with Guzman (30-0-1, 17 KOs) winning a split decision and the title remaining vacant.
In September 2008, Guzman also missed weight for a fight scheduled to headline on Showtime. He was supposed to challenge then-lightweight titleholder Nate Campbell, but Guzman was overweight. Campbell was willing to fight in a nontitle contest, but Guzman refused and the fight was canceled. That caused Campbell to miss a desperately needed $300,000 purse, forcing him to declare bankruptcy a few weeks later.
Dan Rafael covers boxing for ESPN.com. Follow him on Twitter.