Melbourne Cup-winning trainer Mark Kavanagh has been banned for three years and Danny O'Brien has received a four-year suspension after their horses tested positive for cobalt chloride.
Kavanagh, who trained Shocking to Melbourne Cup success in 2009, was given the ban by the Racing Appeals and Disciplinary Board in Victoria on Wednesday.
His sanction surrounds the horse Magicool while O'Brien's ban comes after Caravan Rolls On, Bondeiger, De Little Engine and Bullpit exceeded permitted cobalt chloride levels.
The vet at the centre of the scandal, Dr Tom Brennan, was hit with a five-year suspension.
Cobalt boosts performance in horses by generating more red blood cells to carry oxygen through the body and allow them to perform to the maximum level without suffering fatigue.
The trio are all appealing the bans to the Victorian Civil and Administrative Tribunal.