Medical cannabis may reduce opioid doses by 64-75% for chronic pain, but evidence is weak | Research

The takeaway

A systematic review of 9 studies (7,222 participants) found a 64-75% reduction in opioid dosage when combined with medical cannabis for non-cancer chronic pain, but all studies had high risk of bias.

Pain medicine clinicians, addiction specialists, and opioid prescribing policymakers.

64-75% opioid dose reduction, but all 9 studies had high bias risk

What the researchers found

Across 9 studies involving 7,222 participants, combining medical cannabis with opioids was associated with 64-75% reduction in opioid dosage for non-cancer chronic pain. Between 32-59% of patients reported using cannabis as an opioid substitute. One study showed trends toward fewer hospital admissions and ED visits. However, all studies had high risk of bias.

Why it matters

The opioid crisis makes any strategy to reduce opioid use critically important. These findings suggest medical cannabis could play a role in opioid dose reduction, but the evidence quality is insufficient to make firm recommendations.

The numbers in context

9 studies; 7,222 participants; 64-75% opioid dose reduction; 32-59% used cannabis as opioid substitute; all studies high risk of bias.

How the study worked

Systematic review of 9 studies (RCTs, cohort, cross-sectional, case reports) from Ovid/Medline, PsycINFO, PubMed, Web of Science assessing medical cannabis effects on opioid dosage in non-cancer chronic pain, using ROBINS-I and AXIS bias tools.

What this study cannot tell us

All 9 studies had high risk of bias; heterogeneous study designs; cannabis doses and products varied; optimal cannabis dose unknown; systematic review was not pre-registered.

How to read the evidence

Moderate: systematic methodology but limited by uniformly high bias risk across all included studies.

When this study was published

Published 2020.

The bigger picture

The potential for 64-75% opioid reduction is striking but must be tempered by the uniformly high bias risk. If confirmed by rigorous RCTs, cannabis-assisted opioid reduction could significantly impact the opioid epidemic.

Questions still open

Would a well-designed RCT confirm the 64-75% opioid reduction? What are the long-term outcomes of cannabis-opioid co-therapy?

Common questions

Can medical cannabis replace opioids for chronic pain?

This review found 64-75% opioid dose reduction when cannabis was added, and 32-59% of patients used cannabis as an opioid substitute. However, all studies had high risk of bias, so the evidence cannot yet support firm recommendations.

Is this strong enough evidence to change prescribing practices?

No. The authors explicitly state the evidence "cannot be relied upon to promote medical cannabis as an adjunct to opioids." More rigorous studies are needed.

Read the original research

Medical cannabis for the reduction of opioid dosage in the treatment of non-cancer chronic pain: a systematic review.

Systematic reviews, 9(1), 167

View on PubMed ↗Publisher’s paper ↗

Citation

Okusanya, Babasola O; Asaolu, Ibitola O; Ehiri, John E; Kimaru, Linda Jepkoech; Okechukwu, Abidemi; Rosales, Cecilia. (2020). Medical cannabis for the reduction of opioid dosage in the treatment of non-cancer chronic pain: a systematic review.. Systematic reviews, 9(1), 167. https://doi.org/10.1186/s13643-020-01425-3