The practice of mixing sleeping pills with alcohol and energy drinks is widespread in the National Rugby League, a club doctor has told the ABC.

John Mayhew, the doctor for the Auckland-based New Zealand Warriors, says he also believes the problem exists in other codes.

His comments come as the NRL begins testing players for the sleeping pill Stilnox and other prescription drugs, in addition to existing tests for 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.

"Basically they get a high and it doesn't contravene any of the existing drug testing protocols," Dr Mayhew told 7.30.

He said that after discussions with players and other club doctors, he believed "cocktailing" sleeping drugs with energy drinks and alcohol was "widespread" in the league.

"It's a problem in Sydney, to a lesser extent in New Zealand, and certainly the non-Sydney clubs as well," he said.

What is Stilnox? Prescription drug used to treat insomnia and some brain disorders

Prescription drug used to treat insomnia and some brain disorders Sometime prescribed to athletes who are having trouble sleeping before big events

Sometime prescribed to athletes who are having trouble sleeping before big events Prescribing it to Australian Olympians was banned just before the London Games

Prescribing it to Australian Olympians was banned just before the London Games Recreational users take Stilnox and deliberately resist its sleep-inducing effects

Recreational users take Stilnox and deliberately resist its sleep-inducing effects Doing so can induce a feeling of a 'high' as well as visual effects

Doing so can induce a feeling of a 'high' as well as visual effects Its recreational use has been reported by other elite sportspeople including cyclists

"Widespread is the word I'd use. I think it's a problem which is involved in the NRL and also, following discussion with people in other codes, it's a problem in other codes as well."

Sam Sorrenti, a spokesman for the NRL Doctors' Association, says sleeping drug abuse is not common in the league, but "we would rather stop it before it becomes a problem".

The NRL has not formally banned Zolpidem, the generic name for Stilnox, which is also sold under the brand names Ambien, Intermezzo and Stilnoct.

However, under a new policy club doctors will no longer prescribe it, and if a player returns a positive test, he will initially be counselled against using it.

"If they test positive for a second time, the full brunt of the law will be applied to them," Dr Sorrenti said.

Given Zolpidem is not prohibited under World Anti-Doping Agency rules, it is unclear exactly what sanctions could apply.

Dr Sorrenti says the NRL will likely move to formally ban Zolpidem next year.

NRL chief operating officer Jim Doyle said testing for Zolpidem and depressant drugs Benzodiazepines this season is for data gathering purposes only.

"We want to find out if we do have a problem with prescription drugs in rugby league because, at present, there is only anecdotal evidence," Doyle said in a statement.

“By the end of the year we will know if prescription drugs are being abused in our game and we can take steps to remedy the problem."

Stilnox abused by Australian swimming stars

Stilnox has gained notoriety within the sporting world because of its abuse by a number of Australian swimming stars.

Grant Hackett's manager said the Olympian had been admitted to rehab in the United States earlier this month because of a dependency on Stilnox.

His former coach Denis Cotterell told 7.30 he believed use of the drug contributed to Hackett's failure to win a gold medal at the Beijing Olympics.

"He won't say so and he doesn't look for excuses but I feel for sure it did," he said.

After the men's 4x100m relay team admitted to taking Stilnox in a bonding session ahead of the London Olympics, it was revealed that swimmers competing at an international level had been regularly prescribed the drug to help them sleep.

"You do that continuously for 10 years of your career [and] it's impossible, if the substance you're taking happens to be addictive, [that] you're not going to be addicted to it," Cotterell said.

Swimming Australia's doctors no longer prescribe Zolpidem, and the body supports the Australian Olympic Committee's ban of the drug.

Sports physician backs use of sleep aids for 'wired' athletes

However, some sports physicians argue that sleep aids have a legitimate role in elite sport.

Among them is Dr Peter Larkins, a sports physician and former Olympian who has worked with AFL players and other elite athletes for decades.

"Athletes are often wired up, they are balancing a lot of things, certainly the night-time training and the night-time competitions," he said.

"They often say they replay the competition in their head. They just don't get the rest, and unless you are going to meditate or count sheep, sometimes doctors will give them, in the short term, a sleeping tablet to help them get settled into their normal sleeping pattern.

"[The NRL effectively banning Zolpidem] is an over-reaction because of bad behaviour of a few individuals."

But prominent GP and former head of the Australian Medical Association, Professor Kerryn Phelps, says athletes [should] "stay right away from Stilnox".

Professor Phelps says she has seen multiple patients who have all experienced dangerous effects from Zolpidem, such as sleep-walking on high-rise balconies, and says a full ban on the drug for the general population should be considered.

"The potential side effects are potentially life-threatening. It has been attributed to deaths, and I think we need to be very careful about balancing risks with benefits," she said.

However, Dr Larkins says if doctors are prescribing Zolpidem responsibly, and patients are taking it for short periods only, there should not be a problem.

"Clearly it's got side effects... but that manifests itself so quickly that you stop using it and find the alternative," he said.

"It's the people that are habitually using Stilnox the wrong way that have given it its bad reputation."

Sanofi, the company which makes Stilnox, says last year its "adverse event reporting centre directly received 24 individual reports of suspected adverse events from consumers taking Sanofi's Zolpidem products".

"This represents a ratio of less than 0.01 per cent of packs sold," a Sanofi spokesperson said.