Dr Antony Mersiades, who is a Clinical Trials Fellow at the University of Sydney’s NHMRC Clinical Trials Centre said the current situation illustrates “the challenges of managing community demand for access to such products, and highlight the importance of conducting appropriately designed clinical trials”.

Previous trials of cannabinoid products containing tetrahydrocannabidiol (THC), cannabidiol (CBD) or synthetic derivatives have been compromised by small sample sizes and outdated control arms, Mersiades and colleagues wrote.

One in particular was reported to show “a promising efficacy signal and tolerable psychological adverse event profile” despite the fact that one of the seven patients who received the active drug withdrew due to “transient psychotic symptoms”, say the MJA authors.

“The Therapeutics Goods Administration guidance documents conclude that use of medicinal cannabis for CINV is experimental, and should only be considered for the management of intractable symptoms where standard therapies are ineffective,” they wrote.

A clinical trial is currently underway in New South Wales to determine the efficacy, safety and cost-effectiveness of using medicinal cannabis to prevent chemotherapy-induced nausea and vomiting.

The CannabisCINV trial is being conducted by the University of Sydney, the Chris O’Brien Lifehouse and other leading NSW cancer centres, and is funded by NSW Health. The trial has recruited over 60 of 80 planned participants for its phase 2 trial, with expansion to a 250-participant phase 3 trial planned if phase 2 results are encouraging.

“The results of such clinical trials will provide guidance to clinicians regarding appropriate use in specific indications, product selection, dosage and titration, and appropriate monitoring of both efficacy and safety,” Dr Mersiades said.

Professor Iain McGregor, psychopharmacologist and Director of the Lambert Initiative for Cannabinoid Therapeutics at the University of Sydney, said a 2017 review by the US National Academy of Sciences, Engineering and Medicine had given medicinal cannabis a “gold star” for its efficacy in CINV.

However, he said, many of the 28 studies evaluated in the review were conducted more than 30 years ago, so more up-to-date clinical trials were needed.

Learn more

Medicinal cannabis and nausea: the wait for good evidence - MJA Perspective.