#199 Missing “High” Quality Evidence: Medical Cannabinoids for Pain?
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- Any chronic pain: Systematic review of systematic reviews.1
- Pain reduction (15 Randomized Controlled Trials (RCTs), 1,985 patients): 39% versus 30%, Number Needed to Treat (NNT)=11.
- Larger (>150 patients) and longer (9-15 weeks) RCTs: No effect.
- Mean pain improvement ~0.5 (0-10 scale, not clinically meaningful).2
- Pain reduction (15 Randomized Controlled Trials (RCTs), 1,985 patients): 39% versus 30%, Number Needed to Treat (NNT)=11.
- Neuropathic pain:
- Inhaled MC (five RCTs, 178 patients):3 NNT=6.
- Any MC (15 RCTs, 1,619 patients):4 NNT=14.
- Cancer pain (six RCTs):5 Pain reduction not statistically significant.
- HIV neuropathy, smoked MC (two RCTs, 89 patients):6 NNT=4.
- Multiple sclerosis pain (seven RCTs, 298 patients):7 Mean pain improvement over placebo ~0.8 (0-10 scale, borderline clinically insignificant).
- Acute pain (seven RCTs): One positive, one negative, and five equivalent to placebo.8
- Versus medications: Cannabinoids no better with more adverse events (versus low-dose amitriptyline)9 or inferior with similar adverse events (versus dihydrocodeine).10
- No difference in Quality of Life.2,4,5
- Very sparse evidence for back pain, fibromyalgia, or osteoarthritis.11-13
- Issues:
- Cannabinoids generally adjunctive to other pain treatments.1,2
- Quality often poor: Of 28 RCTs, two low risk of bias and 16 high risk.2
- When assessed, unblinding common, likely exaggerating effectiveness.6,14
- For inhaled marijuana, data on pain is very sparse and poor:1
- Only five RCTs with 189 patients followed 6 hours to 12 days.
- Represents <1% of the total patient-years studied of MC for pain.
- Prescribing guidance available through the College of Family Physicians of Canada15 and multiple reliable sources,16-19 including international sites (example20).
- Health Canada provides clinician21 and patient information.22