The Newcastle Knights back, who represented New South Wales in the 2007 State of Origin series, had appealed to the NRL's anti-doping body in March after a four-year ban was recommended by the Australia Sports Anti-Doping Authority (ASADA).
The basis of the 30-year-old's appeal was that he had used the drug not for competitive advantage but to help with his recovery from a series of serious hamstring injuries.
The NRL's anti-doping tribunal confirmed the ban on Wednesday, leaving Mullen 21 days to appeal to the Court of Arbitration for Sport.
"ASADA will continue to work to protect those athletes who make the right decisions when it comes to injury treatment and rehabilitation," ASADA chief executive Ben McDevitt said in a statement acknowledging the ban.
"Ultimately, Mr Mullen has paid a heavy price for his poor decision making."
(Reporting by Nick Mulvenney, editing by Amlan Chakraborty)
Share
