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Lowered Pain Tolerance From Opioid Use

Dragana Komnenov PhD
Ball of opioids rolling down a hill over people

Lowered pain tolerance and the destructive cycle of chasing pain relief is a hallmark of opioids. Cannabis offers consistent pain relief without the risk of developing increased pain sensitivity.

When opioids first hit the market in 1911, and up until the 1990s, these were reserved for post-surgical (acute) pain and patients with cancer. Since then, opioid use for treatment of chronic pain has escalated. It is now one of the most over-prescribed medications in North America. Unfortunately, one of the most common side effects of long-term opioid use is sensitization to pain, or a decrease in pain tolerance. In other words, instead of acting as an analgesic and decreasing pain, overused opioids make individuals more sensitive to pain.

Ball of opioids rolling down a hill over people

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Patients on high doses of opioid pharmacotherapy may suffer escalating acute pain, which can lead to a vicious cycle of increasing the dose, but never again finding that pain relief. Currently, there are no strategies that would prevent, reverse or manage this state of increased pain sensitivity.

To put this sensitization issue into perspective, one study pointed out that patients with lower back pain, on long-lasting morphine, developed pain tolerance within one month of therapy. Further studies suggested that one of the culprits for this process involved a metabolite of morphine, called morphine-3-glucoronide.

Cannabis Grow op indoor

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Cannabis Research on Pain is Not Very Accurate

Cannabis is an alternative analgesic and anti-inflammatory medicine, as demonstrated by a several pre-clinical studies. However, when it comes to human trials, the data is very scarce and the available studies are inconclusive due to inherent design flaws. Most of the studies conducted, thus far, measured pain tolerance and pain threshold immediately after consumption of THC, CBD, or both (via smoking or oral formulations). Collectively, these studies suggest that cannabis has some analgesic effect but only in males, and not in females, and can increase the pain sensitivity and decrease pain threshold. Not exactly reliable results when you consider methodologies.

Confused red-head girl looking to the side

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Recent data from British Columbia sought to clarify the effects of cannabis on pain tolerance by looking at individuals who were regularly consumed cannabis, but this study did not measure pain sensitivity immediately after use. Researchers reasoned that the psychoactive effects of cannabis include perceptual changes, so individuals may perceive pain stimulus in an enhanced way. Due to the increased attention following consumption of cannabis, there is a high probability that subjects are reporting false outcomes because the study did not correct for this.

Cannabis Does Not Increase Sensitivity to Pain

In the end, researchers observed no association between increased pain tolerance and consistent cannabis use. This suggests that, unlike opioids, cannabinoids do not have the potential to heighten pain sensitivity with sustained use. If this is the case, cannabinoid-based pharmacotherapy would be far more superior to opioids.

Man holding 2 points of pain on his back

Image Credit: Albina Glisic

Why Does Opioid Overuse Cause Decrease in Pain Tolerance?

Disturbances to the main neurotransmitters in the brain, caused by over-exposure to opioids, may be causing the increased pain sensitivity. One of the key neurotransmitters involved is glutamate, and it has been shown that with sustained morphine administration, glutamate transporter system becomes inhibited. This leaves more glutamate circulating in the brain, resulting in enhanced pain perception. Additionally, prolonged morphine use has been associated with neurotoxicity.

close up of cannabis nugs

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Cannabis is superior in its pain relief action without decreasing pain tolerance, because receptors for the endocannabinoid system can be found in the spinal cord and these respond to cannabinoids. Another reason for the difference could be that opioids act at the level of the brain and cannabinoids at the spinal cord. Certainly there is important use for opioids, and that is in treating acute pain for the short term. Patients risk addiction, however, if they are using opioids for chronic pain relief; cannabis is a much better option.



Dragana Komnenov
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