The off-contract prop on Thursday received a two-month suspension and $27,500 fine after twice testing positive for cocaine.

Slipper has been battling depression and had Thorn's blessing prior to Christmas to limit his training schedule as he helped his mother in her battle with cancer.

While Thorn said his compassion remained with Slipper, the hard-line coach insisted after Saturday's tight loss to the Highlanders that it didn't excuse the Wallabies and Reds favourite's indiscretions.

"It's a tough one because obviously Slips has been struggling and there's some compassion around that and caring for that and supporting that," he said.

"The other side is, cocaine - you can't have that.

"As a head coach of the club, I've got all my young guys in here, Queensland Rugby, watching my sons play rugby at school.

"For me I don't want to let down those mums and dads and these young guys."

Thorn's Reds lost 18-15 to the Highlanders at Suncorp Stadium on Saturday and, now a distant third in the Australian conference, are unlikely to feature in the Super Rugby finals.

It means Slipper may have played his last game at the club he has stood by since 2010.

The coach says he hasn't had a chance to consider if Slipper will be offered another contract after celebrating his 100th Super Rugby cap at the club earlier this season.

But Thorn has already shown his hand, keeping Karmichael Hunt on the outer since his own cocaine-related dramas earlier this year.

"There's two sides ... supporting him and the attention he needs and also the side of all the kids playing rugby ... you can't have that (drug use)," he said.

"It's a matter of addressing that (contract) stuff down the track."

Lifeline 13 11 14

beyondblue 1300 22 4636

Australian Associated Press