The head of the Canadian Armed Forces says the military is reassessing the use of an anti-malarial drug that can cause serious psychiatric side-effects now that Health Canada agrees the brain damage associated with mefloquine can be permanent.

Whether to continue prescribing the preventive medication to Canadian troops sent to tropical countries has become an urgent matter as Canada prepares for a three-year peacekeeping commitment in Africa. Some veterans say mefloquine ruined their lives and blame it for violence on the 1992 mission to Somalia, where Canadian troops killed a 16-year-old Somali.

Countries including the United States recognized years ago that mefloquine can cause permanent brain damage. In August, Health Canada quietly adopted an advisory for doctors, pharmacists and patients that the drug can cause adverse neuropsychiatric reactions "that have been reported to continue many years after mefloquine has been stopped."

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Read more: Defence Minister puts onus on troops while defending use of harmful malaria drug

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"It is certainly an emerging issue," General Jonathan Vance, the Chief of Defence Staff, told The Globe and Mail on Tuesday. The controversy over mefloquine is not new, he said, but "it goes without saying that, if Health Canada is coming out with a statement like that, then we ought to be concerned. So it certainly has my full attention."

Gen. Vance said Brigadier-General Hugh MacKay, the Surgeon General of the Canadian Armed Forces, is looking into the situation "even as we speak," and the military will use a scientific approach as it decides what to do next.

Later on Tuesday, when asked by The Globe and Mail for comment, Brig.-Gen. MacKay would say only that "we're going to look at all the evidence about mefloquine and make a decision based on that." He said his study has no timeline.

Although other anti-malarial drugs are now the more common choice of Canadian soldiers, mefloquine is still prescribed five times as often to Canadian military personnel as it is to their U.S. counterparts.

Symptoms reported by users include anxiety, paranoia, depression, hallucinations, psychotic behaviour and, in rare cases, thoughts of suicide. Studies suggest only a few mefloquine users have long-term problems, but the rate of significant, permanent damage is unknown.

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Gen. Vance said that "if anybody's harmed or injured as a result of their military services, we have procedures for [dealing with] that."

But some of the soldiers who were forced to take mefloquine in Somalia, Rwanda and Afghanistan say it has been impossible to get proper a diagnosis because their symptoms closely resemble post-traumatic stress disorder. Doctors say treatments for PTSD can be detrimental to those with mefloquine toxicity.

Some veterans are calling for an inquiry to determine what role the drug might have played in Somalia, where 900 military members were required to take it in a poorly monitored clinical trial. They also want the government to contact anyone who was prescribed mefloquine to determine if they have suffered long-term consequences. And they want more research to develop better diagnosis and treatment.

On Monday, Defence Minister Harjit Sajjan said troops now make their own informed choice about whether to take mefloquine or an alternative when they are deployed to a country where malaria is prevalent. But that was not always the case.

Francis Harrison, who was a military police corporal on the Canadian mission to Rwanda in 1994, says he was ordered to take mefloquine. "I have lived a life of psychological roller coaster since," he said, "and this needs to be investigated deeper."

Mr. Harrison said his superiors told him that, while most of the troops would take their pills on Tuesdays and Thursdays, he would take his on Saturdays so he would be capable of keeping the peace when the others were experiencing the side-effects.

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"We used to call them Wacko Tuesday and Psycho Thursday," Mr. Harrison said. "The dreams and the nightmares, just the way people reacted, it made me really question what the hell was going on. But no one ever said anything."

The U.S. military considers mefloquine the drug of last choice, and the U.S. special forces have banned it.

Robert Menendez, a Democratic senator from New Jersey, wrote to his government's Defence and Veterans Affairs departments two weeks ago to say that "given the widespread use of mefloquine and the potentially long-lasting symptoms among those administered the drug, it is important for both the Department of Defence and the Department of Veterans Affairs to develop a plan to deal with what could become a significant health crisis among the veterans population."

In Australia, concern is intense from media and the public over the damage that may have been done to soldiers who took mefloquine in a clinical trial.

And in Britain, after a lengthy public inquiry, more than 500 former British military staff who were prescribed mefloquine are considering whether to launch a lawsuit alleging the Ministry of Defence failed to consider the dangers of the drug.

Drug regulators in Canada, Europe and the United States agree that mefloquine causes mental health symptoms that last decades after use, said Remington Nevin, a doctor at the Johns Hopkins University Bloomberg School of Public Health in Maryland who has studied the drug's effects for nearly a decade.

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"The experience of Canadian veterans," Dr. Nevin said, "makes this painfully obvious to all but those few officials who continue to manufacture doubt, seemingly in a misguided attempt to avoid liability and responsibility for a preventable problem that they mostly created for themselves."