Some pet owners in Manitoba are paying more than double what they could be spending on medications, a CBC News investigation has found.

In some cases, the owners could be saving money on pet medications if they buy them at pharmacies rather than at veterinary clinics.

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This prescription for Tyson, Stuart Ritterman's cat, was purchased at a Winnipeg Safeway pharmacy, not at a veterinary clinic. (CBC)

The CBC News I-Team found that prices for 100 tabs of amitriptyline, a prescription drug that helps pets with behavioural problems, ranged between $20.90 and $29.85 at several Manitoba veterinary clinics.

The same drug can be purchased for as little as $11.30 at a Winnipeg Costco store, or $18.80 at a Safeway pharmacy.

"We don't pretend to compete with the Wal-Marts and the Costcos," says Dr. Phillip Schott, who runs the Birchwood Animal Hospital in Winnipeg.

"They have much bigger buying power, much greater clout negotiating with their wholesalers."

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Schott said while there is a fee guideline for veterinarians can follow, it's voluntary, so clinics can vary in their pricing.

"I can say we're probably high on some things and we're low on other things," he said.

Stuart Ritterman says he refuses to go to his veterinarian to buy medication for Tyson, his 17-year-old cat.

Ritterman said he gets Tyson's prescription filled at a Safeway store instead.

"The prescription just says 'Tyson' and then it says 'Cat,'" he said.