Sydney - Australia's Olympic athletes must agree to having their bags and other possessions searched by team officials who on Friday introduced a new ban on sleeping drugs from the day they are selected for Rio.
The hardline stance comes in the wake of swimming great Grant Hackett seeking treatment last year for addiction to the prescription drug zolpidem, sold as Stilnox in Australia.
Members of the nation's swim team also came under scrutiny at the 2012 London Olympics after some took the sleeping tablet at a pre-Games camp.
The Australian Olympic Committee introduced a ban on "certain hypnotic medications", including Stilnox, three weeks before the London Olympics, but has decided to tighten the rules even further.
"First and foremost we banned Stilnox before the London Games because of serious concerns for the welfare of the athletes," said AOC chief executive Fiona de Jong.
"We felt then we had an obligation to protect our athletes from serious harm and that remains our priority today.
"By introducing the ban from the date of selection we are giving any athlete taking hypnotic medications time to wean themselves off the drug long before they enter the (athlete) village in Rio (in 2016)."
Stilnox is a sedative-hypnotic drug used to treat insomnia, with athletes sometimes previously prescribed it if they were having trouble sleeping before big events.
Athletes have admitted it was also occasionally used as a substitute for alcohol that was once traditionally consumed at team-bonding sessions.
All those selected for Rio must agree to the ban and sign a document permitting team officials to search their bags or other possessions in the Olympic village.
"It includes the right to seize any suspicious substance they might find and have that substance analysed and investigated," the AOC said.
If they do not agree, athletes could be expelled from the team and deemed ineligible for future Olympics.
The ban covers medications including zolpidem, which is found in Stilnox and is sold as Ambien in the US and elsewhere; nitrazepam, contained in the brand name Mogadon; and flunitrazepam, found in the brand name Rohypnol.