Cooper contributed to Australia's bronze medal effort in the mixed 4x100 metres mixed medley relay at the Tokyo 2020 Olympics, and was part of the team which took silver in the same race at the International Swimming Federation (FINA) World Championships in Budapest last month.

The 18-year-old won gold at the Australian National Championships in the men's 50m and 100m backstroke in May, and bronze in the men's 50m butterfly.

His time of 24.44sec was an Australian national record.

Cooper had been part of a team training camp in the French city of Chartres, but Swimming Australia announced that he has been sent home for disciplinary reasons.

"Cooper has been sent home from the Dolphins training camp following some well-being challenges, including the use of medication," the governing body said.

"He has acknowledged his mistakes and accepted the consequences, and Swimming Australia will continue to support him as he addresses these challenges.

"The welfare of our athletes remains our absolute priority.

"Swimming Australia is vigilant in educating athletes of their obligations under the National Integrity Framework and will continue to provide all necessary support to ensure they uphold the highest standards and behaviours when representing Australia."

According to The Sydney Morning Herald, Swimming Australia has denied that Stilnox, used to treat insomnia, was the medication in question.

Prior to the London 2012 Olympic Games, six swimmers were fined by Swimming Australia for using the drug during a "bonding session".

Commonwealth Games Australia chief executive Craig Phillips said the organisation was awaiting further details on Cooper's case.

"We have received advice from Swimming Australia, but at this stage we don't have the detail around that," Phillips said.

"There has been speculation about that particular, so we are waiting for more information from Swimming Australia hopefully today on the situation.

"[It is] obviously a difficult decision to take.

"I know that they certainly have some concerns for Isaac's well-being as well, so really at this point we don't have any more detail than the media speculation that has been around."

Australia's Chef de Mission for Birmingham 2022 Petria Thomas offered her best wishes to Cooper as he returns to home.

"We've received some advice from Swimming Australia, we're just looking to clarify some of that before moving forward really," Thomas said.

"It's obviously a challenging time for young Isaac, and we wish him all the best back in Australia.

"It becomes really a well-being matter, and we wish Isaac all the best while he takes the time to work on his well-being."

Cooper had been due to compete in the men's 50m and 100m backstroke, 50m butterfly and 50m freestyle on what would have been his first appearance at the Commonwealth Games.

He was ranked eighth in the men's 50m backstroke final at the FINA World Championships, making him the top performing Commonwealth athlete in the race.

Australia's reigning men's S9 100m freestyle and SB7 100m breaststroke Commonwealth Games champion Tim Disken has also been ruled out of Birmingham 2022.

Swimming Australia said this was due to "a setback in his recovery following recent surgery".

Disken won silver at the Tokyo 2020 Paralympics in the men's 4x100m medley 34 points relay, following on from three medals at Rio 2016 including gold in the men's S9 100m freestyle.

Swimming and Para swimming events at Birmingham 2022 are due to be held at the new Sandwell Aquatics Centre from July 29 until August 3.