Officials analyzed 365 samples of pills seized between June 2007 and July 2008 by police in Montreal, Laval and Longueuil.

Ecstasy and methamphetamines, or speed, which are sold under names such as Coca-Cola, Toyota, NHL, On-Star and Couche-Tarde, are the most popular forms of so-called designer drugs in Quebec, police say.

But according to the study, 54 per cent of the pills tested did not contain what they were supposed to.

"People — they just don't know what they are taking," said Benoit Archambeault, manager of Health Canada’s drug analysis service. "For ecstasy consumers, for example, about 80 per cent of people buying ecstasy aren't getting ecstasy — they're getting something else."

In some cases, more than two different drugs were found in one pill. This can lead to addiction or other health problems because the combined effects of the drugs have not been studied, Archambeault said.

Officials said the goal of the study was to help inform the public about the dangers of illegal drug use.

The use of designer drugs by teenagers is a growing concern, said Sgt. Suzanne De Larochelière, a drug specialist with Quebec provincial police. Studies indicate 10 per cent of high school students in Quebec use amphetamines, officials said.

"It's kind of a new trend," De Larochelière said. "It is easy to take and easy to carry, too."

Most designer drugs are made in makeshift labs using recipes found on the internet, officials said.