Does Marijuana Use Affect Acute Pain Management Following Traumatic Injury?

“Cannabis is the single most versatile herbal remedy, and the most useful plant on Earth. No other single plant contains as wide a range of medically active herbal constituents.” – Dr. Ethan Russon

The legalistaion of marijuana and its health benefits has been a hot topic for debate worldwide.  Past studies have demonstrated medical benefits of the plant, which are largely antinociceptive (i.e. block the detection of a painful or injurious stimulus via sensory neurons), in treating chronic and neuropathic pain [1,2].  However, few studies have looked at the effects of marijuana use and abuse for acute pain management.  This is important to understand if the legalistaion, and therefore use, of marijuana is to occur.  A recent pilot study has explored the association between pre-injury marijuana use and pain response following traumatic injury [3].

Study Methods

This study investigated to see whether there were any differences, by marijuana use, in total opioid analgesics consumed and average daily pain scores in patients admitted to a hospital from a motor vehicle collision.  The arrival blood alcohol concentration, injury mechanism (i.e. car crash, motorcycle crash), injury severity score, substance use and clinical outcomes were abstracted from the study population.  Also, the results from the standard multi-drug UDS panel were recorded.  Chronic marijuana use was defined as daily, or almost daily, use or more than 1 ounce of marijuana in the last month.  Whereas any other form of marijuana use was defined as episodic.

The study population was categorised into two groups: those that tested positive for drug use (i.e. amphetamines, benzodiazepines, cocaine, methamphetamine, or opiates) and those that tested negative.  The effects of marijuana usage in these groups were analysed by opioid analgesic consumption – used to dull pain – and pain score tests

Screen Shot 2018-07-17 at 23.38.05
Fig.1[3]: Average daily opioid consumption consumed by marijuana (MJ) use in non-drug (a) and drug users (b)

Non-Drug Users

91% of the test population tested negative for drugs.  In this group, marijuana users received significantly more opioid analgesics compared to non-marijuana users (Fig.1a).  However, there was little difference in opioid consumption between chronic and episodic marijuana users.

Marijuana users reported significantly higher pain scores in comparison to non-users, with episodic user scores being higher than chronic users and non-users (Fig.2a).

Drug Users

9% of the test population tested positive for drugs.  Results from this group show that opioid consumption was not significantly different between drug users that also used marijuana compared to drug users who didn’t use marijuana.  Relative to episodic and non-marijuana use, drug users that chronically used marijuana reported highest opioid analgesic consumption (after adjusting for age, cause of injury and injury severity score).

Pain scores in this group were not significantly different between marijuana users and non-users.  However, further analysis of frequency of marijuana use shows that drug users that didn’t use marijuana reported higher pain scores.

screen-shot-2018-07-17-at-23-37-59.png
Fig.2[3]: Average daily pain numeric rating scale scores by marijuana (MJ) use in a non-drug users and b drug users

Implications of the Study

The findings of the study would suggest use and abuse of marijuana causes a lower pain threshold and sensitisation to acute pain – indicated by higher pain scores and increased opioid administration up to 37% more than non marijuana users.  However, marijuana doesn’t affect acute pain management in user of drugs such as cocaine, amphetamines, opioids etc.

Several cannabinoids function to suppress pain by binding of CB1 and CB2 receptors, causing inhibition of norepinephrine release from sympathetic nerve terminals and pain relief [4].  However, these antinociceptive effects may respond to neurogenic, inflammatory and chronic pain better than acutely evoked pain.  This has been shown in studies, where cannabinoid binding to CB1 receptors would provoke pain sensitisation and increasing the risk of turning acute pain into chronic pain [5].  Therefore, it could be possible that marijuana is useful in treating chronic pain, but detrimental in treating acute pain.

These findings are important due to the increasing marijuana use, especially if it is to be legalised.  Specifically, the results suggest that patients using marijuana have special consideration during acute pain management.  However, this is just a pilot study and the topic and underlying mechanisms must be looked into more thoroughly.

— By Ross Green

References

1. Wilsey B, Marcotte T, Deutsch R, Gouaux B, Sakai S, Donaghe H. Low-Dose Vaporized Cannabis Significantly Improves Neuropathic Pain. The Journal of Pain. 2013;14(2):136-148.

2. Fine P, Rosenfeld M. The Endocannabinoid System, Cannabinoids, and Pain. Rambam Maimonides Medical Journal. 2013;4(4).

3. Salottolo K, Peck L, Tanner II A, Carrick M, Madayag R, McGuire E et al. The grass is not always greener: a multi-institutional pilot study of marijuana use and acute pain management following traumatic injury. Patient Safety in Surgery. 2018;12(1).

4. McPartland J. The Endocannabinoid System: An Osteopathic Perspective. The Journal of the American Osteopathic Association. 2008;108(10):586.

5. Pernia-Andrade A, Kato A, Witschi R, Nyilas R, Katona I, Freund T et al. Spinal Endocannabinoids and CB1 Receptors Mediate C-Fiber-Induced Heterosynaptic Pain Sensitization. Science. 2009;325(5941):760-764.

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