Australian Nursing and Midwifery Federation state secretary Neroli Ellis told a parliamentary inquiry it was heartbreaking to watch cancer patients endure vomiting and nausea without being able to care for them fully with treatments currently available.

Ms Ellis said research showed positive effects of medical cannabis far outweighed potential risks.

"As patient advocates we are convinced a safe clinical trial of medicinal cannabis is in the best interests of Tasmanians," Ms Ellis said.

"We see it as an opportunity for therapeutic gains as well as an opportunity for further research and evidence to be garnered."

The Alcohol, Tobacco and Other Drugs Council also supported a Tasmanian trial, with ATDC chief executive Jannette Smith warning MLCs against focusing on legislative barriers.

"It would be a shame if Tasmania did not take the opportunity to show some leadership in the area," Ms Smith said.

"We have so many well informed, interested people and the skills and capabilities in our research institutes well worth taking advantage of."

Ms Smith said she was no more concerned about medicinal cannabis finding its way onto the black market than about existing misuse of prescription drugs.

However, leading oncologist Ray Lowenthal later outlined limitations of completed trials and challenges of future ones.

"If you look at [existing] trials we often have 13 or 21 patients whereas for a thorough trial of a new drug we're talking about hundreds," Professor Lowenthal said.

"It's very hard to draw conclusions when you're dealing with such small numbers."

Professor Lowenthal told MLCs any medical cannabis trial must be held in conjunction with interstate and overseas partners.

"There is no way in the world, in my opinion, you could do a thorough and meaningful trial of a drug in Tasmania alone," he said.

"I don't want people to go rushing off and doing futile trials that waste time, energy and money doing something where you don't receive any useful information in the end."