The use of caffeine stimulants and sleeping tablets among AFL players is a non issue, says Brisbane Lions coach Michael Voss.

He says caffeine tablets such as No-Doz are not performance enhancing and advice on using sleeping pills is best left to a doctor.

"I'm not 100 per cent sure what the issue is," Voss said on Friday.

"I did (use caffeine tablets) for a while and found no benefit from it whatsoever.

"I just don't really see what this issue is.

"We have doctors and they are there and play a critical role in what we do.

"I put my trust in them."

Richmond veteran Ben Cousins was admitted to a Melbourne hospital in a semi-conscious state on Monday after an adverse reaction to a sleeping pill.

There was also speculation Cousins had taken caffeine tablets before the club's win over Sydney on Sunday.

Voss said caffeine was a legal substance.

"The last time I checked, a 12-year-old could still buy coffee at a coffee shop," Voss said.

He questioned if using caffeine as a stimulant worked.

"You don't know whether it (caffeine) works or it doesn't.

"These are all the little things you do as an athlete whether it's altitude training or whether it's No-Doz or caffeine or whatever it happens to be.

"It's not performance enhancing, that's a different discussion, so I don't really see it."

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