The Warriors doctor John Mayhew has told the ABC that the practice of mixing sleeping pills with alcohol and energy drinks is widespread in the National Rugby League.
Mayhew says he also believes the problem is rife in other codes.
His comments come as the NRL begins testing players for the sleeping pill Stilnox and other prescription drugs, in addition to steroids and other performance-enhancing substances.
When taken with energy drinks or alcohol, sleeping drugs can produce an amphetamine-like high, without falling foul of anti-doping rules.
Mayhew says cocktailing sleeping drugs with energy drinks and alcohol is common in the NRL.
The NRL has not formally banned Zolpidem, the generic name for Stilnox, which is also sold as Ambien, Intermezzo and Stilnoct.
However, Sam Sorrenti, a spokesman for the NRL Doctors' Association, says under a new policy club doctors will no longer prescribe it, and if a player returns a positive test, they'll initially be counselled against using it.
Sorrenti says if they test positive for a second time, they'll face the full brunt of the law.
Zolpidem is not prohibited under World Anti-Doping Agency rules, making it unclear exactly what sanctions could be imposed.
The NRL is considering formally banning Zolpidem from next year.