New questions are being raised about the safety of a drug used to treat attention-deficit hyperactivity disorder amid reports that more than 40 Canadian children have attempted suicide after taking it.

The issue highlights a long-brewing debate over the decision to prescribe powerful drugs to treat complex psychiatric problems among children.

"It does raise some concerns," said Roger McIntyre, head of the Mood Disorders Psychopharmacology Unit at Toronto's University Health Network.

"Childhood psychiatric disorders, I think, are an area [that] in and of itself remain a controversial topic."

Health Canada said it received 189 reports of adverse reactions associated with atomoxetine, sold under the name Strattera, from the time it was put on the market in February, 2005, to the end of last year.

The reports included 55 suicide attempts - 41 of which were among children aged 6 to 17, and 12 that were adults between 18 and 45. Ages were unavailable in two reports, according to information published by Health Canada in its quarterly publication on adverse drug reactions.

Of the 55 suicide attempts, one patient died, three had not yet recovered, and 29 had recovered. The outcome was unknown in 22 reports.

It is not the first time concern has been raised about Strattera, and other ADHD drugs. In September, 2005, just months after the drug was put on the Canadian market, Health Canada warned that the drug may trigger behavioural changes or increase the risk of self-harm. A year later, it issued a warning that all ADHD drugs may be associated with agitation, hallucinations and other psychiatric problems among children.

One expert said the problems associated with this category of drugs should prompt serious questions about the fact they are often prescribed to young people with ADHD.

"The drugging of children for attention-deficit disorders is very controversial," said Alan Cassels, a drug policy researcher at the University of Victoria. "You might say, 'Why is this being prescribed at all?' "

Another serious issue is the fact many parents, and even some doctors, may be unaware that certain drugs have been associated with problems, Mr. Cassels said. That's because such warnings are often not well publicized and may not reach the ears of parents who must make the crucial decision about whether to put their child on powerful medications.

"If you're a parent and your kid gets prescribed Strattera, do you know that drug comes with a risk of attempted suicide?" he said.

Many children may require medication to manage the symptoms of ADHD, according to Dr. McIntyre, who is also a psychiatry and pharmacology professor at the University of Toronto. But such disorders often coincide with other underlying psychiatric conditions that have not yet been recognized or diagnosed. As a result, ADHD medication could inadvertently trigger a suicidal reaction or other severe behavioural problems, he said.

It's important for parents to inform themselves about the risks of a particular drug so they can look for any warning signs, Mr. Cassels said.

Eli Lilly Canada, which makes Strattera, declined to provide a spokesperson to respond to questions yesterday. But the company provided a written statement saying that Strattera is not the only stimulant-type ADHD treatment that has been associated with behaviours related to suicide. The company said more than five million people worldwide have taken the drug since it was approved.

"Lilly continues to actively monitor and evaluate all new safety data sources as they become available, and will take prompt and appropriate action based on new findings in accordance with established risk-management principles," communications manager Jennifer Gordon said in a statement.