High-Potency Medicinal Cannabis Prescribed Routinely in Australia Despite Limited Safety Data

A recent review reveals that physicians in Australia frequently prescribe high-dose medicinal cannabis, with concentrations reaching up to four times the THC levels tested in clinical trials.

Researchers at Monash University assessed the existing evidence regarding the efficacy and safety of higher-potency medicinal cannabis products prescribed in Australia. THC, or delta-9-tetrahydrocannabinol, serves as the primary psychoactive component of cannabis.

In Australia, there is no regulatory cap on the THC concentration permitted in medicinal cannabis products. Higher-dose formulations, including dried herb and concentrated extracts—categorized as Category 5 products—range from 13% to 88% THC.

Out of over 1,000 available medicinal cannabis products, only two have undergone pre-market evaluation for quality, safety, and efficacy by the Therapeutic Goods Administration (TGA), the national drugs regulator.

The review’s co-author, Professor Suzanne Nielsen of the Monash Addiction Research Centre, noted that she and her colleagues examined studies assessing the effectiveness of medicinal cannabis across various conditions, discovering that only products with up to 22% THC had been tested.

“When examining randomized controlled trial evidence—the strongest evidence available for determining a product’s efficacy for a given condition—we identified a significant mismatch between the available evidence and the products currently being prescribed and used,” she said.

The findings were published in the journal Drug and Alcohol Review.

Nielsen recommended that the TGA consider establishing THC concentration limits at or below the levels naturally occurring in the cannabis plant, approximately 35%, “or even at 22% in line with what has been tested in trials.” She also suggested implementing health warnings, improved labeling, and enhanced screening and monitoring of potential harms.

“It remains unclear how well consumers actually understand the products they are using,” she added.

According to TGA data, chronic pain and anxiety are the primary drivers of prescriptions, with Category 5 products accounting for half of all approvals.

This is despite research indicating that medicinal cannabis is no more effective than placebo in reducing anxiety symptoms, noted Dr. Jack Wilson of the University of Sydney’s Matilda Centre for Research in Mental Health and Substance Use.

“Regarding chronic pain, a 2018 review concluded that there was low-quality evidence suggesting cannabis may be associated with minor pain reductions,” Wilson stated. “Further research is needed, specifically studies that incorporate real-world doses and products.”

Nielsen noted that while medicinal cannabis prescriptions historically tended to take the form of oral oils, approvals in recent years have dramatically shifted toward high-THC smoked or vaporised dried flower.

“This shift does not align with the evidence for what actually works,” she said. “Moreover, there is very limited evidence in general regarding medicinal cannabis, particularly concerning these high-concentration THC products and inhaled forms.”

A TGA spokesperson informed Guardian Australia that 27 cases involving medicinal cannabis have been voluntarily reported to its adverse events database thus far in 2026, though a report does not confirm that the product caused the adverse symptoms.

An analysis of 614 medicinal cannabis adverse event reports submitted to the TGA between mid-2022 and mid-2025 found that half were related to Category 5 products. These included acute harms such as psychosis, cannabis hyperemesis syndrome (characterized by cycles of nausea, vomiting, and abdominal pain following long-term use), and suicidal behaviour.

Wilson expressed concern that these products might delay or replace evidence-based treatments. “Regular consumption of THC is also associated with an increased risk of short- and long-term harms, potentially worsening the patient’s condition,” he said.

A 2025 review of cannabis prescribing by the Australian Health Practitioner Regulation Agency (Ahpra) uncovered concerns among medical regulators that “profits are being prioritized over patient safety in some medicinal cannabis prescribing practices.”

The Ahpra review identified practitioners who had individually issued more than 10,000 prescriptions for high-strength THC medicinal cannabis products within six months, and highlighted cases of consultations lasting only a few seconds.

Wilson asserted that with the rise of telehealth clinics and direct-to-consumer marketing, “suppliers are clearly prioritizing profit over patient health.”

Guardian Australia has contacted the Royal Australian College of General Practitioners for comment.

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