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Health Canada is revising its prescribing and patient information for all ADHD drugs in Canada to add the “potential for psychiatric adverse events.”

These have included rare events of agitation and hallucinations in children, spokesman Paul Duchesne said Thursday from Ottawa.

ADHD, or attention deficit hyperactivity disorder, is a neurobiological disorder that is marked by poor attention, impulsivity and hyperactivity. Left untreated, children with the condition may have behaviour problems and trouble learning in school.

Up to five per cent of Canadian kids are believed to have ADHD. Last year, more than two million prescriptions for the drugs were written in Canada.

Government officials are conducting an ongoing review of ADHD drugs and are discussing updated labelling with manufacturers, which should be completed by December, Duchesne said.

“Canadians taking ADHD medication should consult with their doctor if they have any questions or concerns,” he said, noting that patients should never stop taking ADHD medication without consulting with their doctor.”

Canadian adverse drug reaction reports from 2000 to 2005 list about two dozen cases of mood, personality and psychological reports among ADHD drug users, but there is no way of knowing whether the drugs caused the problems. There were three suicides.

Dr. Umesh Jain, a child psychiatrist who is head of the Canadian ADHD Resource Alliance, said Thursday that Health Canada is right in its message that doctors should “be cautious, be prudent” — but he doesn't think the advice is anything new.

A properly diagnosed patient on ADHD drugs, taking the correct dosage, would not have a problem with agitation and hallucinations, he said.

“Because what's happening is you're taking the patient to a normalization state with the medications. When medications are diverted and abused, they are potentially at risk for developing hallucinations, delusional beliefs, etc.”

The new ADHD medications are long-acting, once-a-day preparations and have “low diversion potential,” said Dr. Jain, who works at the Centre for Addiction and Mental Health and Toronto Hospital for Sick Children.

“If you were somebody who was going to use an excess amount, well beyond that of the range of the ADHD profile, yeah, they can potentially cause those problems.”

He said Health Canada is trying to be cautious in alerting the population about all potential risks — “partly I think because the medications are being so widely used.”

Dr. Jain said the Health Canada statement will likely cause some patients to be worried.

“We have to find ways of calming our patients down and say ‘Look, these aren't going to cause you hallucinations and delusions in the doses that we prescribe to you,' ” he said.

It's the second revision to the patient information on ADHD drugs this year. In May there was a warning that identified heart-related risks associated with ADHD drugs.

At the time, Health Canada advised Canadians not to use Strattera, Dexedrine, Ritalin, Ritalin SR, Concerta, Attenade, Biphentin and Adderall XR if they have moderate to severe high blood pressure, heart disease or abnormalities, hardened arteries or an overactive thyroid gland.