AUSTRALIAN experts hope legislative reform and more trials will pave the way for informed use of medicinal cannabis, despite new research showing evidence of its benefits in many conditions is at best of moderate quality and in many cases is weak.
Professor David Penington, former head of the University of Melbourne’s medical school and university vice-chancellor, said legislative change in Australia enabling state-based, regulated supply would allow open-label trials investigating the benefits and side effects in people accessing medicinal cannabis.
“Medicinal cannabis is not at the point where one can expect doctors to write prescriptions. It has not been sufficiently tested in terms of dose-response relationship and relationship of dose to side effects, or interaction with other medications for it to be formally regarded as a therapeutic substance”, Professor Penington told MJA InSight.
“Having said that, there are a lot of data … that suggest there are benefits from medicinal cannabis under certain circumstances. Many of the claims are not based on good evidence, but some are based on good evidence that provides a basis for proceeding.”
Last week JAMA
published a systematic review and a clinical review outlining the evidence base, pharmacology, indications and adverse effects of the medical use of cannabinoids. (1) (2)
The systematic review analysed 79 trials (6462 participants) and found moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain and spasticity, but only low-quality evidence of benefit in chemotherapy-related nausea and vomiting, weight gain in HIV infection, sleep disorders, and Tourette syndrome.
An accompanying editorial said the US was putting “the cart before the horse” in its approach to medicinal cannabis, and advised waiting for high-quality evidence before its use was more widely adopted. (3)
In the US, medicinal cannabis can be legally used in more than 20 states, but there are inconsistencies in how patients with specific conditions qualify for medicinal cannabis use in and between the states.
Professor Penington said the JAMA reviews were useful, but were primarily based on the US experience and did not consider a sufficient number of international publications.
He said the papers did not mention the important role that cannabinoids might play in Dravet and Lennox-Gastaut syndromes — distressing forms of epilepsy in young children — now accepted by the US Food and Drug Administration as a basis for an orphan drug trial. Families with children who currently received benefit “deserve continued access to medicinal cannabis”, Professor Penington said.
Next year NSW Health will start a clinical trial investigating the benefits of medicinal cannabis for children with severe, drug-resistant epilepsy. (4)
In last week’s NSW state budget, $9 million over 4 years was earmarked to fund a trial for this indication and two others: adults with terminal illnesses and chemotherapy-induced nausea and vomiting. Queensland and Victoria have pledged their support for the three trials.
Earlier this year, Professor Penington wrote in the MJA
that Australia was “behind the times” in its approach to medicinal cannabis. (5)
However, he said it was a quickly evolving area, with political and community will growing towards change.
“We ought to work with the politicians to be sure it works sensibly”, Professor Penington told MJA InSight. “I hope the medical profession will take the trouble to be part of that rather than just recoil and say ‘we don’t want to write prescriptions’.”
He said rather than prescribing medicinal cannabis, the doctors’ role should be to provide well-informed advice to patients and to government.
A Senate inquiry into the Regulator of Medicinal Cannabis Bill, to establish an independent regulator responsible for licensing the growing, manufacturing and distribution of medicinal cannabis, was expected to report its findings this month. (6)
Other states and territories are also contemplating legislative reform.
In August, the Victorian Law Reform Commission will report the findings of its inquiry into options for legislative change in relation to medicinal cannabis. (7)
Public Health Association of Australia (PHAA) spokesperson David McDonald said the JAMA systematic review provided guidance for Australian governments as they moved to establish medicinal cannabis programs and highlighted problems in the US approach. “The selection of the health conditions for which legal medical cannabis can be used is a key component of that policy work”, he said.
Mr McDonald said the PHAA, which released a position statement on medicinal cannabis last year, welcomed calls for more and better research into the therapeutic value and adverse effects associated with medicinal cannabis use. (8)
(Photo: Atomazul / shutterstock)