As the Tasmanian Government prepares to spend almost $4 million on a controlled access scheme for medicinal cannabis, some people who already use the drug have raised concerns about the scheme's effectiveness.

The tightly-controlled regulation will mean some Tasmanian patients with severe epilepsy will be able to obtain medicinal cannabis from hospital pharmacies, but there are concerns it will not be affordable for those who need it.

John Reeves already takes medicinal cannabis to relieve his chronic pain and he runs a support group for others doing the same.

Mr Reeves said the drug would be almost five times the price of what is already available on the black market.

"People aren't going to pay the money, they're not going to pay $300 for something they could buy for $50 or grow in their garden," he said.

Tasmania's Health Minister Michael Ferguson said children who had seizures would be the first to be given the opportunity to access the scheme.

"Our first focus under the controlled access scheme is young children and young Tasmanians with drug-resistant epilepsy," he said.

"We don't know at the moment how many children are likely to be prescribed with a medical cannabis product but we want it to be available to those who need it."

Nicole Cowles, whose 11-year-old daughter Alice uses medicinal cannabis, said she had no plans to take her daughter to a specialist doctor in order to access the drug legally.

"The cost of medications to keep Alice where she is currently, at a therapeutic dose, [would be] about $600 a fortnight and that's not something that many families in Tasmania could afford," she said.

Ms Cowles said using the drug had changed her daughter's life.

"At 25 weeks of age Alice was having up to 30 seizures a day and I was told that she was going blind and dying, that she could never survive," she said.

"I started treating her with medicinal cannabis four years ago; from the moment Alice started on the medicinal cannabis her health increased.

"She now has long periods without seizures, [but] it's not just the reduction in seizures, it's the improved quality of life overall."

Mr Reeves said he hoped the scheme would help Tasmanians, but he doubted it would have a big impact.

"I think the horse has well and truly bolted from the Government to be honest," he said.

"They're going to have to make this scheme quite broad, quite open and quite specific for patients needs for it to grow and essentially replace the black, or green, market."

Mr Reeves wanted the Tasmanian Government to make it legal for patients to grow their own cannabis plants for medicinal use.

The Australian Medical Association's Tasmanian president, Stuart Day, said he only supported medicinal cannabis that was prescribed through doctors. 

"We don't believe that black market, self-medicating cannabis is the way to go because essentially you don't know what you're getting," he said.

According to the federal Health Department, medical cannabis cannot be included on the Pharmaceutical Benefits Scheme (PBS) as it was still an unregistered medicine.

A department spokesman said it would welcome the submission of a medicinal cannabis product for evaluation.