CBC's Marketplace tested 50 pharmacies in nine cities across the country to see if they provided required counselling for consumers buying a Schedule 2 drug. (CBC) Many pharmacists may not be conducting important screening required to keep Canadians safe from dangerous drug interactions, a CBC Marketplace investigation reveals.

The more than 38,000 pharmacists across the country fill over half a billion doctor prescriptions every year, but are also required to ensure medications don’t interact in potentially dangerous ways.

In a months-long investigation that's the largest of its kind in Canada, Marketplace took hidden cameras into pharmacies to test if pharmacists are dispensing the proper advice to patients asking for behind-the-counter drugs.

There are more than 38,000 pharmacists across Canada that fill over half a billion prescriptions every year. (CBC) Vince Garnier knows the danger all too well.

In October, a pharmacist in North Sydney, N.S., failed to alert his mother to an interaction between different medications she was prescribed.

“She became very weak, nauseous, headaches, lightheadedness, and to the point where she almost fainted at home,” Garnier says.

She ended up in the hospital with serious complications, and hasn’t fully recovered.

“[My father] broke down and started crying. He honestly believed that my mother was going to die,” he said.

Follow Marketplace’s continuing coverage of this investigation all week on CBCNews.ca The Marketplace investigation, Dispensing Danger, airs Friday, Jan. 23 at 8 p.m. (8:30 p.m. NT) on CBC-TV and online.

Hidden camera investigation

Marketplace tested 50 pharmacies in nine cities across the country: Vancouver, Edmonton, Regina, Winnipeg, Toronto, Ottawa, Gatineau, Que., Montreal and Halifax.

Chain pharmacies, grocery stores, big box stores and independent pharmacies were included in the test.

It's important for a pharmacist to have a comprehensive understanding of what patients are taking before making recommendations. - Jane Farnham, chair of the Canadian Pharmacists Association

In each case, a Marketplace tester asked for a Schedule 2 drug — which do not require a prescription but are kept behind the counter because they require pharmacist oversight — and documented the interaction with a hidden camera.

Some testers asked for Palafer, an iron supplement that can lessen the effect of some antibiotics. Others asked for Tylenol No. 1, which includes the narcotic codeine.

Codeine is addictive and can interact with other medications, increasing the effect of the drug on the system. In the U.S., Tylenol No. 1 is not available without a prescription.

Pharmacists in Canada are regulated by provincial colleges that establish standards of practice. Every jurisdiction requires that pharmacists counsel people who buy Schedule 2 drugs to ensure they are using them appropriately.

But of the 50 pharmacy visits, only 23 provided any kind of counselling and none caught potentially dangerous drug interactions.

More than half — 27 of the 50 stores tested — handed over the drugs with no counselling.

‘Not the norm’

Jane Farnham, chair of the Canadian Pharmacists Association, says counselling is an essential part of the service provided by pharmacists.

“There are a number of medications where it is prudent to have advice from a pharmacist before consuming particular medications,” she told Marketplace co-host Erica Johnson.

'There are a number of medications where it is prudent to have advice from a pharmacist before consuming particular medications,' says Jane Farnham, chair of the Canadian Pharmacists Association. (CBC) “It's important for a pharmacist to have a comprehensive understanding of what patients are taking before making recommendations,” she says

While more than half of the pharmacists tested by Marketplace failed to provide required counselling, Farnham says, “That's not the norm. We pharmacists are committed to providing the highest quality of patient service and responsible patient education.

“If there is an issue or a concern, certainly we really encourage patients and consumers to take it up first with their pharmacist and then if unsatisfied, to take it to the regulatory body in their individual province.”

Later this week: Who’s keeping track of pharmacy errors? Follow the continuing coverage of Marketplace’s investigation on CBCNews.ca.

Have you experienced a pharmacy error? Marketplace wants to hear from you. Email marketplace@cbc.ca.