An addiction doctor has slammed the rush to legalise medical marijuana for sick children, warning there's no evidence it is safe for young brains.
"It shouldn't be used at all on children or adolescents," said Dr Philip Crowley, an addiction medicine specialist at the Royal Adelaide Hospital who will present his views at a medical conference on Friday.
"We now know cannabis is toxic to the developing brain in kids and adolescents. It leads to long-term damage to structures that are vital for memory, learning and thinking."
His comments come as states begin opening up medical cannabis to children with severe epilepsy.
Proponents argue therapeutic compounds from cannabis provide at least some relief for suffering children already with poor development prospects due to illness and for whom other drugs have failed.
International trials with sick children have focused on the cannabidiol (CBD) component of the plant, rather than tetrahydrocannabinol (THC – which has psycho-active properties), although some involve a combination of both.
Fairfax Media understands the medicinal cannabis Victorians have access to will either be pure CBD or have a very high CBD and low THC content.
"There needs to be a lot more studies done on animals, there needs to be evidence that its not going to cause harm," he said, adding that he was worried about both CBD and THC products.
Professor Uri Kramer, a paediatric neurologist who has been running cannabis trials on children in Israel, said the damage the drug could do was "peanuts" compared to the harm caused by severe epilepsy.
About 80 per cent of the 160 children involved in the Israeli trials are clinically retarded, he said. "We're not talking about normal children that I'm giving CBD (cannabidiol), we're talking about children with severe disease. If I'm not controlling the seizures they will be more retarded."
The recent findings from the Israeli study, which involves three hospitals, showed nearly 20 per cent of patients experienced a more than 75 per cent reduction in seizures, while 34 per cent reported at least a 50 per cent reduction.
The Victorian Government has recently legalised medical marijuana and started growing its own crop, which is expected to be available to children with severe epilepsy in 2017.
"The Independent Medical Advisory Committee will use the very best medical evidence available so doctors and families can have confidence in our medicinal cannabis access scheme," a spokeswoman for Health Minister Jill Hennessy said.
"Patients will be closely monitored by a specialist medical team and all possible risks will be taken into account by the (committee)."
In NSW, the government has already started giving children with epilepsy access to an imported cannabis drug, Epidiolex, under a compassionate access scheme and the Queensland Government recently signed a deal to import the same drug.
Dr Crowley will present his views at a meeting of the Faculty of Pain Medicine of the Australian and New Zealand College of Anaesthetists in Adelaide.
The faculty's Dean, Chris Hayes, urged caution as governments race to introduce the drug for extremely sick children. "We should wait and see the results of trials before storming ahead with broader public access," he said.
"It really is about weighing up the benefit and harm."