Ben Cousins is out of hospital and out of AFL action, but out to clear himself from suspicion that illicit drugs were behind his latest health scare.

Richmond player Cousins on Tuesday left the Epworth Hospital after his condition improved from Monday, when he could not be roused after suffering an adverse reaction to a sleeping pill he took Sunday night.

It is believed Cousins also took a caffeine tablet before Sunday's game against Sydney and consumed alcohol that night, but the Tigers insist the 32-year-old's health scare was brought on through a reaction to the sleeping pill.

"Tests have confirmed his condition was the result of a severe reaction to a prescribed sleeping medication," Richmond football manager Craig Cameron said on Tuesday.

The Tigers could not say if or when the Brownlow medallist would play again.

But he is expected to train on Thursday, in the lead-up to Saturday night's game against Fremantle.

Cousins' immediate focus is on proving illicit substances were not behind the latest chapter in his turbulent career.

Richmond said the recovering drug addict had requested he be drug tested by the AFL to prove "beyond doubt" there was nothing illegal in his system.

Cousins' use of caffeine tablets and sleeping pills reignited the debate over whether it was suitable and safe for footballers to use stimulants before games and relaxants afterwards.

AFL football operations general manager Adrian Anderson could not be reached for comment, but confirmed in a statement that caffeine was not a banned substance under the WADA code.

Dr Hugh Seward, executive officer of the AFL Medical Officers Association, said it was not uncommon for players to take caffeine pills before games.

"It's not uncommon for a number of players at any one club to be taking caffeine in one of its many forms before a game to provide a higher level of arousal before a game," he told AAP.

"There has been some medical research in the past which has shown caffeine at moderate to low doses can improve performances in endurance athletes."

Seward said it was also not unusual for players to take both caffeine before games and sleeping tablets after, although players were advised by club doctors on safety issues.

"I don't believe there is a widespread culture of taking uppers and downers to get through a football game and to wind down afterwards," he said.

"I'd discuss the use of both in some detail and only prescribe it if we established together it was wise and safe and didn't cause any adverse consequences."

Seward said he would advise players not to consume any alcohol when taking pills, but said some sleeping tablets could be taken in conjunction with alcohol.

Cousins' scare is set to prompt renewed education among clubs to remind players of the potential dangers of prescribed drugs.

Cameron said Richmond continually counselled players on the issue of prescribed medicine and would "continue to be vigilant to ensure players are well informed".

A spokesman for the AFL Players Association said it was the responsibility of both clubs and players to ensure drug education got through.

The spokesman said the association was "much more concerned about the welfare of players" than what the issue of footballers using prescribed drugs meant for the game's image.

St Kilda star Lenny Hayes admitted he had caffeine tablets before games previously, and likened it to "having a coffee ... it just gives you a little pep up if you're feeling a bit flat".

Essendon coach Matthew Knights said education was vital in ensuring players suffered no ill-effects with prescribed medicine.

"I assume that part of that education is that the alcohol and the mix of caffeine tablets or certain fluids might have an adverse effect," he said.

Knights said he was studying the use of caffeine tablets and sleeping pills on players.

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