The federal government's effort to rein in the cost of reimbursing veterans for their medical marijuana appears to have failed as new figures show Ottawa shelled out a record $75 million in the last fiscal year.

And that is only the beginning: the Veterans Affairs Canada figures show the government is on track to spend nearly $100 million this year as more and more former service members ask the government to pay for their cannabis.

The growing use of medical marijuana by veterans — and the growing cost to taxpayers — comes despite an overhaul of the way the government reimburses ex-military personnel for pot in November 2016.

It was then that the Liberal government reduced the amount of marijuana it would cover from 10 grams per day to three. It also capped the amount it would pay at $8.50 per gram.

The government cited rising costs and a lack of scientific evidence about the drug's medical benefits as the primary reasons for the new restrictions, which were met with anger and concern in the veterans' community.

Veterans Affairs has paid for medical marijuana for veterans since 2008, following a court decision requiring reasonable access to the drug when authorized by a health-care practitioner.

But the number of clients — and the costs — started to explode in 2014 when regulatory changes at Health Canada and a new Veterans Affairs policy established the limit of 10 grams per day.

The government did see its costs decline to $50 million in 2017-18 from $63 million the previous year after the Liberals implemented their restrictions, but those savings were shortlived. The cost jumped to $75 million last year.

The growth can be traced to a more than doubling in the number of veterans asking the government to cover the drug, with 10,000 reimbursed in 2018-19 as compared to 4,500 in 2016-17.

Ten thousand veterans were reimbursed during the first four months of this year alone — 1,700 of whom have special medical exemptions that let them claim more than three grams per day.

Yet at the same time, the scientific evidence about the benefits of weed remains largely incomplete, says Jason Busse of the Michael G. DeGroote Centre for Medical Cannabis Research at McMaster University in Hamilton, Ont.

"We're in a bit of a funny situation where cannabis has emerged on the market as a therapeutic agent not so much because we have rigorous evidence to fully understand the benefits and risks, but more through a series of legal challenges," he said.

What isn't funny, at least not to Busse, is use by veterans and non-veterans alike has continued to increase despite this lack of information as people search for ways to ease chronic pain, post-traumatic stress and other problems.

Many veterans using medical marijuana, such as Michael Blais, who hurt his back as a peacekeeper in Cyprus and is now president of Canadian Veterans Advocacy, swear by its benefits and are angry with the government for cutting the amount it will cover.

"The consequences have been profound," he said Thursday. "It took me two years to get off these frigging Percocets and now I'm back up to five a day. I mean what did they expect us to do? Our pain is relentless."

But while cannabis is different in important ways, Busse compared the current situation to the start of the opioid epidemic, when painkillers were being prescribed without a full understanding of the potential consequences.

"Any time there's a therapy that is being increasingly used where the evidence is limited, I think there should be reason for concern," he said.

"There was this real hope the most powerful analgesics available might provide help for a lot of patients and you saw the prescribing go up considerably year after year. And again, the evidence was thin and it took time to let the evidence catch up."

The federal government has stepped up funding to research medical marijuana in recent years. Some of the money has been directed toward McMaster, which is also home to a new chronic-pain research centre supported by Veterans Affairs. But the science will take time.

"There is some ongoing work that will hopefully be published in the next few years that will give greater insight," Busse said. "Until we have better evidence, it's very difficult to say if use of cannabis is helping, harming or simply ineffective."