A new class of drugs used to treat Alzheimer's disease is sparking growing concerns about possible side-effects, after studies linked one medication to higher death rates.

The drugs – cholinesterase inhibitors – are among the few treatments that have had any success in treating the degenerative brain disease, which affects an estimated 240,000 Canadians over the age of 65.

Earlier this month, the manufacturer, Johnson & Johnson, said a trial of its popular cholinesterase inhibitor Reminyl showed three times as many deaths among patients who were given the drug to treat mild cognitive impairment compared to those who took a placebo.

Muhammad Mamdani

The results have led some researchers to call for a safety review of the whole class of drugs.

"Unfortunately, what happened was 15 people died in the group [taking Reminyl] and five died in the placebo group," said Muhammad Mamdani, a senior scientist with the Institute for Clinical Evaluative Sciences in Toronto.

He's concerned the threefold higher rate of death in the Reminyl trial, which tracked 2,000 patients in 16 countries over two years, might signal problems with all cholinesterase inhibitors.

The drugs are known to affect the heart and many deaths in the Reminyl trial were attributed to heart attack or stroke.

"The effects of the drugs can have vagotonic effects on the heart: essentially, they slow the heart rate down," said Mamdani, a medical professor at the University of Toronto.

"And they can have other cardiovascular effects as well. This has been of some concern to the community. We just haven't realized the magnitude of it."

The trial also indicated that Reminyl is no help in treating mild cognitive impairments.

An advisory issued Jan. 21 by Health Canada warns not to use the drug for any condition other than Alzheimer's. The health watchdog is reviewing information from the Reminyl trial and others using the same class of drugs.

For now, the director of the Memory Clinic at Toronto's University Health Network said he's telling his Alzheimer's patients not to worry.

Dr. Ron Keren, a geriatric psychiatrist, said he's keeping close watch on people who are using the drugs.

"Medications are not candies in a candy store ... Physicians need to be aware of the potential risks and benefits of treatment," he said.

Some patients taking the drugs said they'll continue even if a higher mortality rate is proved because the benefits have been so marked.

Fred West, a Halifax man diagnosed with Alzheimer's disease, said he started getting confused and couldn't even decipher words on a page until doctors prescribed the drug Exelon, also a cholinesterase inhibitor.

"I intend to take my pills every day and just smile every time I take one," West said.

Health Canada hopes to have more conclusive answers by April.