Most doctors won’t exercise their legal right to prescribe medicinal cannabis for chemotherapy induced nausea and vomiting (CINV) until robust evidence is available, experts say.

Writing in a perspective in the MJA Dr Antony Mersiades, a medical oncologist and Clinical Trials Fellow at the NHMRC Clinical Trials Centre at the University of Sydney and colleagues note that recent legislation allows Australian clinicians to prescribe medicinal cannabis for the prevention and management of CINV.

This was despite international and national clinical practice guidelines for the prevention and management of CINV concluding that there was currently “insufficient quality evidence” to recommend medicinal cannabis for routine use in this indication.

A guidance document from the Therapeutics Goods Administration (TGA) published last year also concluded that the use of medicinal cannabis for CINV remained experimental and should only be considered for the management of intractable symptoms when standard therapies had failed.

The authors noted that American Society of Clinical Oncology guidelines for CINV prophylaxis had recently recommended that the antipsychotic olanzapine be added to existing therapies for CINV following the results of a phase 3 trial in which patients taking the medication experienced lower rates of sickness and nausea.

“We argue that evidence from high quality trials similar in design to the olanzapine trial, demonstrating the efficacy and safety of medicinal cannabis for the prevention and management of CINV, is needed before most clinicians are willing to prescribe this class of medications widely in Australian clinical practice,” the authors wrote.

They point to the CannabisCINV study currently underway in NSW which will determine the efficacy, safety and cost-effectiveness of medicinal cannabis to prevent CINV.

The recent legislative changes in Australia “illustrate the challenges of managing community demand for access to such products, and highlight the importance of conducting appropriately designed clinical trials,” they concluded.

“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.”