Twenty-nine critically ill children will be granted early access to a medical cannabis treatment grown by the Victorian Government, it has been announced.

The children, who all suffer from epilepsy, will be granted access to medical cannabis imported by the State Government from Canada.

"To enable this compassionate access, a limited amount of cannabidool oral solution manufactured by Canadian company Tilray... was purchased by the government and arrived in Melbourne late last week," the government said in a statement.

Victorian Health Minister Jill Hennessy told the ABC the children were nominated by paediatric neurologists to receive the treatment and then assessed by a clinical panel.

"We know this medicine can dramatically change the quality of life for some of Victoria's very sick kids," she said.

"This means families will no longer have to make the heartbreaking choice between breaking the law or watching their kids suffer."

The Federal Government last week announced it had approved plans to let domestic companies sell the product, while a series of trials are underway in states across the nation.

Supporters to rally in SA

On Saturday medical cannabis campaigners will gather in SA to protest for easier access to the drug, more than a week after a similar rally was held in NSW.

Campaigners and people who treat their loved ones with the drug say there is still confusion over access to medical cannabis, and whether doctors have the sufficient knowledge of the drug to feel comfortable prescribeing it.

SA woman Jenny Hallam has been campaigning for medical cannabis for years, and in 2014 was raided by police for supplying medical cannabis to patients around the country.

Late last year Hallam joined forces with a Victorian company with the aim of having a legal version of her medical oil available to patients in that state by the end of the year. She said the company applied for a licence to grow cannabis for medical purposes last year.

"We're still waiting," she said.

"We could start growing now."

She told the Huffington Post Australia that since federal health minister Greg Hunt's announcement last week, she has been inundated by requests for the drug by people she can't help.

"They are coming to my house," she said

"It's breaking my heart having people begging for their lives."

Hallam, who never charged money for her oil, said there was initial excitement about the federal government's announcement, but she fears it won't help people already being treated by domestically sourced products.

She said black market prices for the drug are getting higher since Australia started moving towards legalising medical cannabis, with a gram of cannabis oil costing as much as $200 compared to $160 just six months ago.

Some patients undergoing chemotherapy require up to a gram a day, she said.