The IRB have confirmed USA wing James Paterson has been banned for four months after testing positive for a banned painkiller at the Rugby World Cup.
The Highlanders wing will be able to return on February 13, 2012 after his suspension was backdated to October 13, 2011.
Paterson tested positive for the painkiller Oxycodone - a substance which is on the WADA Prohibited List.
The IRB said that Paterson injured his shoulder earlier in the tournament and took the painkiller to play in his team's last pool match against Italy on September 27.
"This was a very unfortunate case in the sense that it could have been avoided by referencing the WADA Prohibited List which is provided to all Unions and was proactively made available to all participating teams and players prior to and during RWC 2011," said IRB Anti-Doping Manager Tim Ricketts.
"The main message to come from this error is that all medical personnel and Players must be diligent in checking all medications whether it be over the counter or prescription medicine to ensure it does not contain any prohibited substances. Under the strict liability principle a player is responsible for any prohibited substance found in their system."