Industry experts have hit back at research which claims CBD is ineffective in treating back pain.
The CANBACK study, published by the Medical Journal of Australia, found cannabidiol did not reduce pain or length of hospitalisation for people with acute low back pain.
However, critics have said the researchers erred by focusing on CBD to the exclusion of THC and for drawing data from patients with many drugs, including opioids, in their system before being given cannabidiol.
Austin Health researchers set out to assess the analgesic efficacy and safety of single-dose oral CBD as an adjunct to standard care for patients presenting to an emergency department with acute, non-traumatic low back pain.
Patients who presented between May 2018 and June 2019 were randomised to receive 400mg of CBD or a placebo, in addition to standard emergency department analgesic medication.
The researchers wrote: “Mean pain scores at two hours were similar for the CBD (6.2 points) and placebo groups (5.8 points). The median length of stay was nine hours for the CBD group and eight-and-a-half hours for the placebo group. Oxycodone use during the four hours preceding and the four hours after receiving CBD or placebo was similar for the two groups, as were reported side effects.”
“The CBD and placebo groups did not differ with respect to hospital length of stay, adverse effects, and additional opioid medication use.
“Given its high cost, this is an important finding for patients who may consider requesting Therapeutic Goods Administration (TGA) approval for access to CBD.
“It is imperative that the medical utility of CBD and other cannabis products, their side effects, and how these products interact with other medications, be investigated in well-designed studies.
“[Our] trial was the largest clinical investigation of CBD for treating people with acute low back pain, one of the few to examine the effect of CBD without tetrahydrocannabinol on acute pain, and was undertaken in a setting representative of clinical management of acute back pain in emergency departments.
“We found that CBD was not superior to placebo as an adjunct medication for treating low back pain in this setting.”
Posting on the InSight+ website, Associate Professor Vicki Kotsirilos AM said: “CBD alone is generally not prescribed for pain. THC is usually the component used for pain in medicinal cannabis products with CBD and requires more research.
“My personal clinical experience is medicinal cannabis containing THC and CBD (not CBD alone) when used cautiously can be of help with the management of chronic pain, particularly neuropathic pain eg. trigeminal neuralgia, and in some patients with fibromyalgia, when all other treatments are exhausted or of limited use due to side-effects etc.”
Meanwhile, Professor Iain McGregor from the Lambert Initiative told InSight+ CANBACK’s focus on acute – rather than chronic – low back pain, was “not particularly useful in light of the way CBD is being used in the broader community”.
“Most people with a knowledge of CBD would not be suggesting its use for an acute exacerbation of pain that is serious enough to warrant an emergency department visit,” he said.
By contrast, chronic back pain was the second most common cause after anxiety for Australians accessing medicinal cannabis – either under prescription through the Special Access Scheme or illicitly – according to the Institute’s CAMS20 survey.
“What we really want is [a randomised controlled trial] involving chronic administration of CBD versus placebo over several weeks in stable patients,” said McGregor.
He added the fact most of the patients already had many drugs including opioids in their system before being given CBD was a major problem with CANBACK.
“I am not sure how you are supposed to look for a clean CBD signal under such conditions,” he said. “If anything, the study shows that nothing much works for acute back pain, including CBD.”
The Dean of ANZCA’s Faculty of Pain Medicine Professor Michael Vagg insisted the study was “a small step towards addressing the critical lack of evidence as to how CBD in particular might be worth using”.
“The study design allows adequately for demonstration of benefit if it was to be found. In particular, it is impressive that the funding and conduct of the study was done in a health care setting, not by industry,” he added.