Why league players mix prescription drugs and energy drinks

League bosses have every reason to be concerned about players mixing prescription medication and caffeine-laced energy drinks.

Various medical reports say there can be moderate to severe reactions when the two are combined.

The effects can range from increasing caffeine's effects which causes headaches, high blood pressure and insomnia, to potential life-threatening side effects.

It depends on the doses and which medicine has been taken - in the case of the five Warriors it has not been established by the Herald what prescription drugs were ingested but they were being used in combination with energy drinks.

There are a number of reported reasons why sports people take the cocktail - a main one is replicating recreational drugs without running foul of the law and/or anti-doping rules.

Two years ago, Warriors doctor John Mayhew said he believed the practice of mixing sleeping pills with alcohol and energy drinks was widespread in the NRL. "I believe the problem is quite prevalent in the NRL, of mixing Stilnox, benzodiazepines with alcohol and caffeinated drinks," he told the ABC.

Radio Sport's Kent Johns talks to NZRL CEO Alex Hayton:

Last year, South Sydney players Dylan Walker and Aaron Gray were hospitalised and placed into induced comas after overdosing on a variety of prescription painkillers.

In response, the NRL welcomed an offer from South Sydney club to pilot hair follicle testing for prescription drugs. The NRL said it had been conducting more than 2000 tests a year to discover whether the misuse of prescription drugs was an issue and if further action was required.

Last week, Kiwis and Parramatta star Kieran Foran accidentally overdosed and was taken to hospital. The problem hit the Kiwis team at the 2013 World Cup, when the prescription drug Stilnox, used to treat insomnia, was identified as the being used by some players with energy drinks. Resisting its sleep-inducing effects - in this case with the caffeine-laced drinks - was reported to produced a high. In 2014, the NZRL changed its rule so it could test for prescription drugs and take whatever action it felt appropriate.

In rugby, All Blacks Cory Jane and Israel Dagg took sleeping pills on a "boozy" night out at the 2011 World Cup. Jane later said the incident had been "scary", and the pair couldn't recall what happened after they had taken the cocktail of drink and drugs. New Zealand Rugby has asked sports doctors to report any knowledge of similar abuse.