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Injections of Synthetic THC Can Significantly Reduce Acute Pain, Review Finds

By Leo Bear-McGuinness

Published: Mar 24, 2020   
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Intramuscular injections of cannabinoids can relieve acute pain more effectively than oral cannabis treatments, a new systematic review has found.

Published in Cannabis and Cannabinoid Research, the review of six randomized-controlled clinical trials (RCTs) concluded that both types of cannabis treatment ensued a small but significant reduction in subjective pain scores when compared with placebos in patients experiencing acute pain.

Straight to the pain

Pain relief is one of the most oft-cited reasons patients seek out medical cannabis. But despite this demand, the clinical evidence base for marijuana’s ability to reduce acute pain – a temporary but distressing pain secondary to tissue damage – isn’t great.

One review of the clinical evidence in 2017 concluded that “on the basis of the available randomized controlled trial evidence, cannabinoids have no role in the management of acute pain.”

But the new Cannabis and Cannabinoid Research review somewhat challenges that verdict.

“There is low-quality evidence that cannabinoids have a small but statistically significant reduction in acute pain in the clinical setting,” the authors wrote in their conclusion.

To make their judgement, the authors assessed six RCTs in a systematic review with a meta-analysis.

In total, 678 participants were involved in the trials. Most studies had tested the effects of pharmaceutical-grade cannabinoids, such as the synthetic THC drug Levonantradol, on patients recovering from surgery. Two studies of the studies were deemed to have a low risk of bias, while three studies were found to be at moderate risk, and one at high risk, of bias.

After reviewing the results, the authors found that the trial involving an injection of synthetic THC showed significantly stronger pain-relieving results than the trials using orally administered cannabinoids, such as nabilones. The authors say this difference isn’t surprising, considering that cannabinoids are subjective to significant first-pass metabolism in the liver, which further reduces their bioavailability.

Adverse events and limitations

Many participants experienced unpleasant side effects during the trials; those in the cannabinoid groups experienced more cases of nausea, dizziness, and vomiting. But most side effects were considered “nonserious,” which led the authors to give the cannabinoids an overall favorable safety profile.

The researchers also noted that the trials had their limitations, such as small sample sizes and variation in the dosage, timing, duration, and route of cannabinoid used. So, to further clarify the usefulness of cannabinoids in relieving acute pain, more clinical studies with uniform conditions will be needed.

“Our review highlights the need for further research to investigate the optimal route and composition of cannabinoids in the acute pain setting, including large, high-quality randomized clinical trials, to better understand the risks and benefits of cannabinoids in this patient population,” the authors wrote in their conclusion.

Speaking to Analytical Cannabis earlier this year, Mike Bennett, a professor of palliative medicine at the University of Leeds, also championed the need for more cannabis-pain studies, as his own review of cannabinoid-cancer pain trials had found the medicines lacking.

“I think there is great interest in cannabinoid medicines from the general public at the moment, but in cancer pain, using this particular product, we can't see a positive benefit.”

“I think, for now, the evidence doesn't support these cannabinoid medicines for the management of cancer pain. But I can imagine that more research using different sorts of cannabinoid products and different outcome measures might need to be done to me more certain.”

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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