"The reality of the fact that you can only get 31 days' supply, and New Zealand law does not allow you to renew that prescription, plus the practicality of going back and forward to get it, I think makes it extremely unlikely."
The country New Zealand is watching closely in terms of medicinal cannabis is Australia, where clinical trials to assess the safety of medicinal cannabis products - not raw cannabis - could start in about six months.
Mr Dunne, who recently met with Australia's Health Minister Sussan Ley, said his understanding was it would be two to three years before those clinical trials concluded.
Once they were, and if the products were approved by Australian authorities as able to be prescribed, it was almost certain that Medsafe in New Zealand would do the same, Mr Dunne said.
"There are trials underway in other countries, but they are at various stages and very limited in nature, and I think the one that offers the most practical prospect of some results within a defined period of time, is Australia."
Mr Dunne said since October he had made it clear that New Zealand would welcome clinical trials, but no companies had been interested.
The mouth spray Sativex is currently the only form of medicinal cannabis currently available in New Zealand, but is not funded by Pharmac and costs about $1300 a month.
Prescriptions are approved by the Ministry of Health. Other products must be approved by Mr Dunne.
Last year, 19-year-old Alex Renton's family campaigned for him to be given medicinal cannabis and in June he was prescribed Elixinol, a cannabidiol made from hemp. Mr Renton died on July 1 at Wellington Hospital after suffering an acute prolonged seizure in April.
Last month Mr Dunne announced that he had asked the Ministry of Health to review the guidelines for considering applications from people wanting to use cannabis products for medical purposes.
Mr Dunne said the guidelines were more recently applied to an application for medical cannabis made on behalf of former Council of Trade Unions head Helen Kelly, but subsequently withdrawn by her oncologist before any ministerial decision was required.
In January, Ms Kelly wrote to Mr Dunne to seek permission to use medicinal cannabis.
Ms Kelly, who has terminal lung cancer, was already using cannabis oil to ease her pain, and said the drug had been "brilliant" for helping with nausea, lost appetite, and pain relief following chemotherapy.
Last month, the ministry responded to her application, saying it would be deferred because it did not contain enough information, to the frustration of Ms Kelly.
Cricketing great Martin Crowe, who died this month from lymphoma, was self-medicating with liquid marijuana in the final months of his life, according to his close friend, former English international Mike Selvey.
The late broadcaster Sir Paul Holmes also turned to marijuana before his death, Lady Deborah Holmes revealed this month.
