COPE: Cannabinoids to Obviate Pain Experiment After Knee Replacement

COPE: Cannabinoids to Obviate Pain Experiment After Knee Replacement

Total knee replacement is a major and painful orthopaedic (joint and bone) surgery where the knee joint is replaced with an artificial joint. It is an effective and successful procedure to treat severe knee arthritis and reduce pain, but many patients report intense pain after the surgery.

Postoperative pain control is predominated by opioids (morphine-based drugs). While opioids are effective to manage the pain, they can have acute and chronic complications, including confusion, nausea, vomiting, constipation and high risk of addiction.

Medical cannabis is an effective and safe alternative for pain treatment. Recent studies showed that patients have reported a reduction in opioid usage when taking cannabis as a substitute for pain relief.

This study aims to investigate whether adding medical cannabis (cannabidiol - CBD) treatment will decrease the amount of opiates needed in the first 2 weeks after knee replacement compared to a group given placebo.

COPE (Cannabinoids to Obviate Pain Experiment after knee replacement) will be a single-centre, prospective, randomized, placebo-controlled, superiority trial, with two parallel groups designed to investigate the effect of cannabis as postoperative pain treatment compared to placebo on total opioid consumption after total knee replacement.

Eligible patients are: men and non-pregnant women aged ≥18 years scheduled to undergo primary total knee replacement. and with no opioid usage within the last 3 months or history of narcotic abuse.

Patients will be recruited at the department of orthopaedic surgery at St Michael's Hospital (Toronto - Canada), and informed consent will be obtained from those eligible. Central computer-generated randomization will be used to randomly assign participants to cannabis or placebo groups (1:1 ratio). Only the study pharmacist will know allocated treatments.

Inclusion Criteria:

• 18 years of age and older
• Men and women
• Patients with radiographic confirmation and clinical correlation for severe osteoarthritis diagnosis with an indication for total knee replacement
• Patients undergoing primary unilateral total knee replacement
• Patient is able to provide informed consent to participation in the study

Exclusion Criteria:

• Pregnancy
• Breastfeeding
• Current opioid use
• Cognitive impairment or mental illness (e.g., dementia, Alzheimer disease and psychoses), which will prevent patients from reliably providing primary outcome data
• Unable to swallow an oral tablet (medication)
• History of opiate, narcotic and alcohol abuse
• Revision total knee replacement surgery
• High risk of falls as determined by the treating physician
• Patients refusing participation
• Pre-existing/ regular cannabis use