Australian doctors are commonly prescribing high-dose medicinal cannabis with THC concentrations far exceeding levels tested in clinical trials, according to a Guardian Australia exclusive published July 29, 2026 (The Guardian). The findings come from a rapid review conducted by researchers at Monash University, published in the journal Drug and Alcohol Review and indexed on PubMed under PMID 41918345.

The review, led by author M Graham and co-authored by Professor Suzanne Nielsen of the Monash Addiction Research Centre, identified 15 studies from around the world examining products consistent with the Therapeutic Goods Administration's Category 5 composition. The maximum THC concentration in those studies was 22%. Professor Nielsen stated that randomized control trial evidence only exists for products containing up to 22% THC. The Monash Addiction Research Centre notes that evidence for THC concentration exists up to 22.6% in a limited range of physical and mental health conditions.

Category 5 medicinal cannabis products in Australia, which include dried herb and concentrated extract, range from 13% to 88% THC. There is no upper limit for THC concentration allowed in medicinal cannabis products under current Australian regulation. The review concluded that no evidence was found on the safety or efficacy of prescribed Category 5 products with THC concentrations above 22% w/w (220 mg/g).

Of more than 1,000 medicinal cannabis products available in Australia, only two have undergone pre-market evaluation by the TGA for quality, safety, and efficacy. The TGA's own website states that most medicinal cannabis products are unapproved therapeutic goods not included in the Australian Register of Therapeutic Goods (ARTG). Since February 2021, the TGA has allowed over-the-counter sales of registered low-dose CBD products that meet standards of quality, efficacy, and safety, a narrow category distinct from the high-THC products now under scrutiny.

Chronic pain and anxiety drive the majority of medicinal cannabis prescriptions in Australia, according to TGA data reported by The Guardian. Category 5 products make up half of all approvals. A TGA spokesperson told Guardian Australia that 27 cases involving medicinal cannabis had been voluntarily reported to its adverse events database so far in 2026. An analysis of 614 medicinal cannabis adverse event reports submitted to the TGA between mid-2022 and mid-2025, published in the Australian & New Zealand Journal of Psychiatry, found that half were related to psychiatric or nervous system disorders.

Professor Nielsen recommended that the TGA consider THC concentration limits at or below 35%, which she noted is naturally occurring in the cannabis plant, or at 22% in line with what has been tested in clinical trials. The Monash Addiction Research Centre made a formal written submission to the TGA regarding cannabis regulation in October 2025. The TGA had announced a planned consultation to address growing safety concerns regarding unapproved medicinal cannabis products in August 2025.

Medicinal cannabis is among the TGA's 2026 priority areas, alongside vapes, weight-loss drugs, and cosmetic procedures. The convergence of the Monash review, the adverse event analysis, and the TGA's own prioritization points to a regulatory framework under strain. A system designed to provide patient access through unapproved pathways now operates at a scale and potency spectrum that the clinical evidence base has not kept pace with. The voluntary adverse event reporting mechanism, with 27 cases logged in the first half of 2026, likely captures only a fraction of real-world outcomes given the volume of prescriptions flowing through Category 5 products.

The broader context here is the gap between Australia's regulatory access pathways and the evidentiary standards that normally govern prescription medicines. When the TGA evaluates a product for inclusion in the ARTG, the agency applies a structured pre-market assessment of quality, safety, and efficacy. The fact that only two of more than 1,000 available medicinal cannabis products have undergone that evaluation means the vast majority of what patients receive has bypassed the most rigorous gatekeeping the regulator can impose. This is not unique to cannabis; the TGA's unapproved goods access schemes exist to address genuine unmet need. What sets the cannabis case apart is the combination of a rapidly expanding patient population, high-potency formulations, and a clinical trial literature that tops out at roughly a quarter of the THC concentrations being dispensed at the upper end of Category 5.

Nielsen's proposed limits anchor the discussion to either a botanical baseline (35%) or a clinical evidence threshold (22%), giving the TGA two defensible regulatory reference points. Whether the regulator adopts either figure, sets a different ceiling, or maintains the status quo will determine how Australia balances therapeutic access against the safety obligations that accompany prescription drug supply. The TGA's planned consultation and its designation of medicinal cannabis as a 2026 priority area signal that the agency is engaging with the issue, though any concrete regulatory output has yet to materialize. The Monash review, submitted formally to the TGA and now published in the peer-reviewed literature, provides the evidentiary foundation for whatever comes next.