A vet named by a former friend and colleague as the source of the substance at the heart of cobalt cases in NSW and Victoria has proclaimed his innocence.

Adam Matthews, a former employee of the Flemington Equine Clinic, has denied he supplied Vitamin Complex to senior partner Tom Brennan who in turn gave it to horses in the Mark Kavanagh and Danny O'Brien stables.

Vitamin Complex was also sent to Sydney trainer Sam Kavanagh who, along with Brennan and Matthews, has appeared before the Racing NSW Appeal Panel this week to fight his disqualification.

The original inquiry was sparked by a caffeine positive and high levels of cobalt found in the Sam Kavanagh-trained Midsummer Sun after he won last year's Gosford Gold.

After Kavanagh named Brennan as the source, he in turn said he got it from Matthews who he said sourced it from Canada.

"I don't know anyone in Canada, I've never had contact with anyone in Canada," Matthews said.

"I have never used Vitamin Complex."

Matthews has also denied being a party to a race-day administration of a drench given to Midsummer Sun by arrangement with harness racing identity John Camilleri.

He admitted putting Sam Kavanagh in touch with Camilleri who he said was looking to buy into imported horses from Europe.

He said Kavanagh asked if Camilleri knew anyone who could drench a horse in his absence and he said he probably could.

"My understanding was it was a post-race recovery drench to be given on the Saturday," he said.

Earlier this week Camilleri also said it was a drench to be given on the Saturday, something he had not said at an earlier inquiry after which he and Mitch Butterfield, the person who gave the drench, were disqualified.

Matthews, who admitted to having a serious gambling problem, said he backed Midsummer Sun as part of a multi bet in the early hours of Friday, January 9 after a night out.

"It was a $1000 three-leg multi I put on at 2.57am," he said.

"That was a small bet for me and I had another multi later that morning."

Matthews was dismissed by the Flemington Equine Clinic after a period of stress leave, while Brennan has stood himself down and is looking to sell his share of the practice.

The Appeal Panel will hear submissions from the two vets and Kavanagh next month.