Police warn two recent cases of counterfeit drugs found in Ontario pharmacies are likely to be followed by more.

"We are seeing counterfeiting becoming a much larger problem than in past years," said RCMP Const. Judy Lawrence.

"Unfortunately, the counterfeiters are counterfeiting items that will now affect people's health and safety, such as pharmaceuticals."

The registrar of the Ontario College of Pharmacists says the arrests of pharmacists on such charges could have started a disturbing trend.

"It was really something that we did not see in Canada," said Deanna Williams. "It was something we considered to be ... unthinkable."

Globally, the counterfeit drug trade is on the rise, particularly on the internet, according to drug regulators and police.

The differences between real drugs and imitations can be subtle.

Health Canada advises consumers to be familiar with the colour, size and shape of the pills they take, and to ask questions if things look or taste differently.

In Hamilton, a pharmacist face charges that he sold counterfeit heart and blood-pressure medication.

Earlier this week, a pharmacist in Richmond Hill, north of Toronto, was in court on charges related to selling imitation Viagra, both at a drugstore and through an online pharmacy.

"It was really alarming for us that happened, and I think it's unrealistic for us to think, if there were two, that those were the only isolated cases we are ever going to see," Lawrence said.

Last month, Health Canada issued an advisory warning people to be cautious if buying the anti-flu medication Tamiflu online.