For Mandy McKnight, the benefits of cannabis oil to treat her son Liam’s debilitating seizures seem almost miraculous — the nine-year-old has gone from being wracked daily by dozens of the life-threatening episodes to having days now when he experiences none.But like many Canadians authorized by doctors to use marijuana to treat a wide range of medical disorders, McKnight is worried what will happen when recreational pot for adults becomes legally available through government-sanctioned retail outlets in July.Will there be enough product to supply both markets? And how will medical users manage the cost, which will be subject to the same excise tax levied on consumers merely looking to get high?“I’m worried about how are they going to guarantee that his medicine is in stock every month and it’s not going to all be bought up by the recreational users,” says McKnight of Constance Bay, Ont., near Ottawa, whose son has dramatically improved since he began taking oral doses of an oil high in CBD (cannabidiol) but low in marijuana’s psychoactive component THC (tetrahydrocannabinol).“Before we started the cannabis oil, he was having upwards on a bad day of maybe 80 seizures a day,” the mother of four says of Liam, who has Dravet syndrome. “There were times when we were calling an ambulance a lot, and he was actually even airlifted into the children’s hospital quite a few times.“It hasn’t freed Liam from disease, but it has certainly improved his quality of life by 1,000 per cent,” she says of cannabis oil, which the family purchases through a licensed producer for $60 per bottle plus GST/HST and shipping costs.Liam’s pediatrician has prescribed 22 bottles per month to treat his seizures, but McKnight admits that she and her husband Dave can afford only half that number.And when the excise tax comes into force once recreational marijuana is legalized, that will add to the financial burden of providing a medicine for their son that isn’t covered under private or provincial insurance.“We’re not low-income,” she says, “and we cannot even come close to affording Liam’s medicine.”Canadians for Fair Access to Medical Marijuana, or CFAMM, has been lobbying the federal government to nip the idea of taxing therapeutic cannabis in the bud, arguing that no other prescription pharmaceutical is subject to taxation.“Affordability is the No. 1 barrier to access for medical cannabis patients and any kind of taxation or price increases will affect patients’ health and fundamentally isn’t how we treat medications from a tax policy perspective in Canada,” argues Jonathan Zaid, founder and executive director of CFAMM.The federal plan would add $1 of excise tax per gram of cannabis or 10 per cent of the final retail price, whichever is higher.MP Bill Blair, the Liberals’ point man on legalizing marijuana, has said his government is committed to maintaining a functional medical marijuana system. But “at the same time, we do not want the taxation levels to be an incentive for people to utilize that system inappropriately and so we propose that the taxation levels for both non-medical and medical will be aligned.”Zaid, who began using medicinal marijuana about four years ago to treat a condition called daily persistent headache, says the government seems to think some people may fake illness to get access to cheaper pot.“While we acknowledge that price differential could be a potential concern, we don’t see that as a reason to disadvantage the 200,000-plus Canadians who legitimately access cannabis for medical purposes,” says Zaid.Health Canada predicts medicinal marijuana users will grow in numbers to 400,000 by 2024. At a time when Canada is battling an opioid dependency and overdose crisis, CFAMM maintains Ottawa shouldn’t be financially penalizing patients who are using a safer alternative to treat their pain — an alternative the organization also believes should be distributed through pharmacies.For Daphnee Elisma of Montreal, cannabis is the only drug that has helped relieve her suffering.A 2010 operation for a brain aneurysm left her with incapacitating migraines, while the removal of lymph nodes during breast cancer surgery in 2014 resulted in the development of complex regional pain syndrome in her right arm.“We’ve tried so many drugs, including opioids,” says Elisma, 42, who spends about $500 a month on oil and dried cannabis, which she primarily ingests through vaping.Unlike recreational users, “I’m not using cannabis on the weekend just for fun and mixing it with alcohol,” she says, balking at the idea that she and other therapeutic users should be hit with the excise duty, which she calls essentially another “sin” tax like that levied on alcohol and tobacco.“I use it out of medical necessity, and that’s what we need the government to understand, to make that clear distinction.”Medicinal users are also concerned about supply, given that many of the country’s licensed producers have indicated they plan to grow and distribute weed for both patients and the recreational market.“Patient groups have expressed concerns that some companies might pivot away from the medical system and focus solely on the consumer system,” says Cam Battley, executive vice-president of Edmonton-based producer Aurora Cannabis Inc.“So we’ve made a commitment that our medical patients come first,” he says, noting that Aurora is part of the industry organization Cannabis Canada, which also wants to see the double taxation on medicinal pot go up in smoke.“It’s morally wrong in our view to tax people who already have a chronic illness and many of whom are already in income-constrained situations.”Minimal insurance coverage — by both private and provincial drug plans — also has medical cannabis users fuming.With the exception of limited coverage for veterans and patients with health spending accounts — discretionary funding that covers such services as chiropractic and massage therapy, for example — most private insurance plans don’t reimburse the cost of medical cannabis. And no province or territory covers the drug under public plans.“There’s less coverage in terms of public-sector coverage, which is extremely unfortunate, given that most patients eligible for coverage by provincial formularies are generally people who have low incomes or are on disability,” observes Zaid.“So these are people who really need coverage the most and they’re getting the least support right now.”McKnight says since Liam started taking cannabis oil, he’s been weaned off all other anti-epileptic medications and has not once been rushed to hospital or admitted due to seizures.“So I think overall we are saving the health-care system thousands of dollars,” she says. “It feels to me as if we’re being punished.”– Follow @SherylUbelacker on Twitter.