Health Canada is asking the manufacturers of Tamiflu to warn consumers of hallucinations and abnormal behaviour, including self harm, as possible side effects.

Manufacturer Hoffmann-La Roche Limited received a similar request from the U.S. Food and Drug Administration last month.

While no direct connection has been established, the caution comes as a result of children and teenagers, primarily from Japan, experiencing such behaviour.

Dr. Colin Lee, co-author of "The Flu Pandemic and You", explained to CTV.ca on Wednesday the reason behind the notice.

"The warning comes from Japan where they certainly use more Tamiflu than we do in North America -- about 10 times more," said Lee. "Just like any other medication or drug there is a surveillance system to look for possible side effects."

Lee said the higher rate of use in Japan most likely accounts for the higher reports of adverse reactions.

"We don't use it very much in general and in children (in Canada) so we may not see it; therefore, it is prudent to look for this possibility," said Lee.

However, he said no definitive connection has been made between the behaviour and the drug.

"They have noted that there may have been an association with about 100 new cases of bizarre behaviour of people who were taking it," said Lee. "They're not sure if it was from the flu itself, but one of the possibilities is an association with taking Tamiflu and these were in children."

Lee said parents should consult with a physician before giving the medication to children.

"Children are not just small adults, the way they metabolize medication... so it's not unusual to see medication that has some side effects in children and not in adults," said Lee.

Other than consulting with a physician, Lee said supervising children on the medication should be enough of a precaution.

"They are having no reports of cases in Canada with such side effects, there is no definite causal link between the medication and these side effects in children," said Lee. 

As of November 11, 2006, there have been 84 reports of adverse events occurring in Canadian patients using Tamiflu, 10 which have proven fatal. A causal relationship has not been confirmed in these cases which did not involve abnormal behaviour or child deaths.

Tamiflu works if taken within 48 hours of getting flu-type symptoms. On average it reduces the length of the sickness by one day. Also, Tamiflu can be used to prevent infection in cases of an outbreak when taken before getting sick.

The drug is different from the flu shot vaccine which has a 70 to 90 per cent effectiveness rate of prevention.