MONTREAL - A report on illegal drug use says more than half of Quebecers who use so-called designer drugs have no idea what they're consuming when they swallow what they think is ecstasy or speed.

It warns users that they're taking a risk if they think they can trust their pusher.

Benoit Archambault, a spokesman for Health Canada, says what jumps out from a report on drug seizures is that in 54 per cent of cases, the user "doesn't really know what he's swallowing."

Archambault made his comment Monday while presenting a report that analyzed all synthetic drugs seized in Quebec between June 2007 and July 2008.

He says substances analyzed in Health Canada laboratories did not always turn out to be what drug dealers claimed.

"For example, in the case of ecstasy, in close to 80 per cent of cases, the user was consuming another drug or a combination of drugs," Archambault said.

"Methamphetamine (speed) was often substituted for ecstasy, making it the number-one synthetic drug in Quebec."

Archambault says 365 drug samples were analyzed and 57 per cent were ecstasy compared with 28 per cent which were methamphetamine.

Two pills which look identical can contain wildly different concentrations of the same substance -- or even different substances.

That means a pill taken at the beginning of an evening might only contain a weak dose of an active substance, while a second pill taken later might contain a very powerful dose.

Dr. Claude Rouillard, of Universite Laval's faculty of medicine, says drug users would be wrong to think they can predict the effect they'll get.

"If it's a young drug user, there's a big chance that person could end up in an emergency room," he said.

Rouillard warns of catastrophic consequences like heart problems or even psychotic episodes.

What's more, he adds, drugs are often mixed with alcohol, energy drinks and marijuana, resulting in a strong cocktail which is potentially even more dangerous.

The report says that, over time, prices have trended downward to the point where a pill now costs an average $10.

The report was released to help mark National Drug Prevention week.