Cannabis products: limited benefit chronic pain

A systematic review of clinical trials with more than 2,300 adults with chronic pain has revealed that cannabis-based products with a higher ratio of tetrahydrocannabinol (THC) to cannabidiol (CBD) They may provide small, short-term improvements in pain and function, especially in people with neuropathy, according to researchers at Oregon Health and Science University.

Despite this, the study indicates that these products are also associated with a increased risk of common adverse effects. Products with a low THC to CBD ratioincluding CBD-only formulations, did not appear to be helpful. The review is published in Annals of Internal Medicine.

The researchers analyzed 25 randomized trials short-term, placebo-controlled studies on cannabis products to update previous evidence on the effectiveness and harms of cannabis-based products for treating chronic pain.

They classified the cannabinoids according to the proportion of THC and CBD (high, comparable, low); whether the product was synthetic, purified or extracted from a plant; and the method of administration (oral, oromucosal, topical). They evaluated its effectiveness in reduction in pain, functional improvement and the presence of adverse effects.

The data showed that the THC-only oral products probably slightly reduce pain intensitywhile the Nabilone cannabinoids showed a moderate effect and dronabinol, null or negligible.

Nabiximols slightly reduced pain intensity and had no significant effect on function. In all trials, products with high and comparable levels of THC were associated with moderate to large increases in adverse effectssuch as dizziness, sedation and nausea. The review highlights the need for more research on long-term outcomes and other types of cannabis products.

An accompanying editorial from the UCLA Center for Cannabis and Cannabinoids (United States) adds that the review highlights both the possibilities and limitations of cannabinoids in the treatment of chronic pain.

Although the THC-based products may offer moderate relief, the discrepancy in study results and concerns about their safety underscore the need for more research to guide patients, doctors, and policymakers.