Soldiers who took a military-issued anti-malarial drug while deployed overseas are prepared to sue the federal government over concerns that the drug may have caused debilitating mental-health side-effects.

Two law firms say will represent military veterans willing to go to court against the government. Lawyers estimate that thousands of Canadian soldiers may be eligible.

John Dowe served with the Canadians Forces from 1990 to 2000 and took mefloquine while deployed in Somalia. Decades later, Dowe said he’s still dealing with side-effects, including anxiety and insomnia.

“It took everything from me. It took away my ability to be bonded with my family and friends. It stole my life,” Dowe told CTV News.

Soldiers who’ve taken the potent anti-malarial drug have complained of a wide range of side-effects including depression, night terrors, aggressive behaviour and suicide.

Some experts believe that some veterans who took the drug may be misdiagnosed with post-traumatic stress disorder.

Canadian government officials said they cannot comment on the pending lawsuits, but said they are monitoring the emerging science on mefloquine. The lawsuits are expected to be filed in the coming weeks.

While in Somalia, Dowe witnessed a teenage boy get beaten to death by a group of Canadian soldiers who were taking mefloquine. Dowe, who was later diagnosed with post-traumatic stress disorder, believes that the drug was instrumental in the killing, widely known as the Somalia Affair.

Advocates have since pushed for a new inquiry to address what role the drug may have played in the Somalia Affair.

Dowe has since founded the International Mefloquine Veterans’ Alliance, which is pushing for military forces across the world to ban the drug.

“We feel used and abused, neglected, and it’s a horrible feeling to have. It makes me mistrust much in society today because of this,” Dowe said.

Health Canada reviewed the potential risk of the drug and, in a report released last year, found there is “limited evidence” that the drug causes “long-lasting and permanent neurological and psychiatric adverse events.”

The once-a-week drug is still authorized for sale in Canada to prevent malaria.

A large number of Canadian veterans who took mefloquine may be diagnosed with PTSD, but may actually have symptoms caused by the drug, according to Dr. Remington Nevin, executive director of The Quinism Foundation, a non-profit dedicated to supporting research and education on the effects of mefloquine and related drugs.

“I would estimate that certainly dozens and possibly hundreds of Canadian veterans have been told they have PTSD when in fact their lasting symptoms are due to nothing more than mefloquine poisoning,” said Dr. Nevin said.

Lawyer Paul Miller, who is representing veterans in one of the proposed lawsuits, said soldiers who’ve taken the drug have suffered life-altering consequences.

“They are have lost their marriages, their kids, they’ve lost jobs, some are homeless. It is horrible what is happening to them, and they need help,” Miller said.

Mefloquine has been the subject of lawsuits before. In the United States, veterans who claimed to have been harmed by the drug are receiving disability compensation. Earlier this year, lawyers for a former American army sergeant argued in court that the drug caused psychosis that was linked to his massacre of 16 Afghan villagers in 2012.

The sergeant, Robert Bales, was sentenced in 2013 to life in prison without parole.

With files from CTV Medical Correspondent Avis Favaro and senior producer Elizabeth St. Philip