How Does Medical Cannabis Impact Opioid Prescriptions for Osteoarthritis?

How Does Medical Cannabis Impact Opioid Prescriptions for Osteoarthritis?

Opioids are a category of medical substances that act on opioid receptors in the human body to produce effects similar to morphine. They are primarily used as painkillers. Whilst there are established benefits of their use for acute pain, there is very little evidence of their effectiveness for chronic pain lasting 3 months or longer. Despite this, and increasing concerns with respect to side effects and dependency, opioids are commonly prescribed for chronic pain.

However, medical cannabis is increasingly being considered as a therapeutic option for chronic pain. In fact, chronic pain is the most reported indication in medical cannabis prescriptions globally. A recent rapid recommendation in the British Medical Journal recommended non-inhaled medical cannabis or individual cannabinoids for chronic non-cancer and cancer pain if first line therapies had proven ineffective. 

While medical cannabis has also been found to have an effect on musculoskeletal pain when compared to placebo, studies are yet to demonstrate a significant improvement when compared to an active comparator. Furthermore, population studies have demonstrated that legalisation of medical cannabis is associated with reduced mortality associated with opioid misuse in specific US States. A recent study aimed to understand the association between medical cannabis use and the utilisation of opioids for the management of chronic pain related to osteoarthritis (OA).

Design and Methods of the Study

Patients with non-spinal, chronic OA diagnoses who were certified for medical cannabis at the Medical Cannabis Department of the Rothman Orthopaedic Institute between February 2018 and July 2019 were prospectively enrolled and included in the study. Inclusion criteria included those patients must have been actively consuming opioids for chronic pain, and OA should be the primary contributor to their pain. Study analysis also excluded patients that had undergone surgery within six months before or after MC certification and that had not been consuming opioids at the time of MC certification. A total of 40 patients were included in the study population. 

Outcome measures were collected at baseline and at three-month and six-month follow-ups using the Patient-Reported Outcomes Measurement Information System (PROMIS) questionnaire. These measures included visual analogue scale (VAS) pain score, Global Mental Health (GMH) quality of life (QoL) score, and Global Physical Health (GPL) QoL score.

Patients were certified for medical cannabis by approved practitioners in the state of Pennsylvania. After the submission of a signed informed consent form, patients were given a prescription for medical cannabis to be filled at state-approved cannabis dispensaries. An oral route of delivery (such as with a sublingual tincture, and/or topical cannabinoids) were recommended over vaporisation; smoking was not endorsed. 

Data on opioid and other controlled substance prescription was gathered using Pennsylvania’s Prescription Drug Monitoring Program (PDMP) system – a state-run program that collects information on all filled prescriptions for controlled substances. Opioid prescriptions were calculated based on the average morphine milligram equivalents (MME) filled per day over the six-month period before and after medical cannabis certification. 

Results of the Study

Primary sites of pain for each patient were the knee (18), shoulder (12), hip (9), or hand (1). Analysis revealed no statistically significant difference in baseline MME/day, VAS pain score, GMH score, or GPH score between patients with different sites of pain.

Collectively, the average MME/day dropped from 18.2 to 9.8 between baseline and six months post-initiation of medical cannabis therapy. Furthermore, 37.5% of patients stopped taking opioid medications; the average drop in MME/day was 46.3%.

These findings upheld the study hypothesis that patients certified for medical cannabis for the management of their chronic OA pain filled statistically fewer opioid prescriptions in the six months following certification than in the six months before it. Significantly, over a third of patients stopped filling opioid prescriptions completely. The level of reduction in opioid consumption is thought to be clinically significant.

Furthermore, patients also experienced improvements in pain and quality of life, as demonstrated by VAS pain scores and Global Mental Health (GMH) quality of life (QoL) score, and Global Physical Health (GPL) QoL score. VAS pain scores decreased by a level considered to be clinically significant at three months but not at six months. 

Adverse Events

Data on adverse events were collected for 25 (52.5%) patients. Most of this sub-group (57.1%) of patients reported that they did not feel intoxicated or high after use of medical cannabis products. Furthermore, of the nine patients that did report feeling intoxicated or high, only three (1.4%) said that it did not interfere with their daily activities, three (1.4%) said that it made their day even better, and three (1.4%) said that they did not like it or that it interfered with their daily activities. 


The researchers conclude that the results of this study support the findings of past literature in this area – that medical cannabis can help reduce the reliance on opioids for the treatment of chronic pain. However, the literature regarding medical cannabis for chronic pain for musculoskeletal conditions remains unclear and very few studies investigate how the use of medical cannabis affects opioid use specifically for chronic pain associated with osteoarthritis.

The authors of this study conclude that, based on these findings, the “the introduction of for patients with low levels of opioid utilisation has a high chance of decreasing opioid utilisation and even eliminating the need for opioid medications to control their pain altogether.” As such, the researchers suggest that medical cannabis should be considered to reduce opioid use in patients with osteoarthritis. Nonetheless, it is also noted that physicians are currently hesitant to prescribe these medications due to uncertainty of their efficacy in addition to limited experience with its use.