Dizziness

Objectives. To evaluate the evidence on benefits and harms of cannabinoids and similar plant-based compounds to treat chronic pain.

Data sources. Ovid® MEDLINE®, PsycINFO®, Embase®, the Cochrane Library, and SCOPUS® databases, reference lists of included studies, submissions received after Federal Register request were searched to July 2021.

Review methods. Using dual review, we screened search results for randomized controlled trials (RCTs) and observational studies of patients with chronic pain evaluating cannabis, kratom, and similar compounds with any comparison group and at least 1 month of treatment or followup. Dual review was used to abstract study data, assess study-level risk of bias, and rate the strength of evidence. Prioritized outcomes included pain, overall function, and adverse events. We grouped studies that assessed tetrahydrocannabinol (THC) and/or cannabidiol (CBD) based on their THC to CBD ratio and categorized them as high-THC to CBD ratio, comparable THC to CBD ratio, and low-THC to CBD ratio. We also grouped studies by whether the product was a whole-plant product (cannabis), cannabinoids extracted or purified from a whole plant, or synthetic. We conducted meta-analyses using the profile likelihood random effects model and assessed between-study heterogeneity using Cochran’s Q statistic chi square and the I2 test for inconsistency. Magnitude of benefit was categorized into no effect or small, moderate, and large effects.

Results. From 2,850 abstracts, 20 RCTs (N=1,776) and 7 observational studies (N=13,095) assessing different cannabinoids were included; none of kratom. Studies were primarily short term, and 75 percent enrolled patients with a variety of neuropathic pain. Comparators were primarily placebo or usual care. The strength of evidence (SOE) was low, unless otherwise noted. Compared with placebo, comparable THC to CBD ratio oral spray was associated with a small benefit in change in pain severity (7 RCTs, N=632, 0 to10 scale, mean difference [MD] −0.54, 95% confidence interval [CI] −0.95 to −0.19, I2=28%; SOE: moderate) and overall function (6 RCTs, N=616, 0 to 10 scale, MD −0.42, 95% CI −0.73 to −0.16, I2=24%). There was no effect on study withdrawals due to adverse events. There was a large increased risk of dizziness and sedation and a moderate increased risk of nausea (dizziness: 6 RCTs, N=866, 30% vs. 8%, relative risk [RR] 3.57, 95% CI 2.42 to 5.60, I2=0%; sedation: 6 RCTs, N=866, 22% vs. 16%, RR 5.04, 95% CI 2.10 to 11.89, I2=0%; and nausea: 6 RCTs, N=866, 13% vs. 7.5%, RR 1.79, 95% CI 1.20 to 2.78, I2=0%). Synthetic products with high-THC to CBD ratios were associated with a moderate improvement in pain severity, a moderate increase in sedation, and a large increase in nausea (pain: 6 RCTs, N=390 to 10 scale, MD −1.15, 95% CI −1.99 to −0.54, I2=39%; sedation: 3 RCTs, N=335, 19% vs. 10%, RR 1.73, 95% CI 1.03 to 4.63, I2=0%; nausea: 2 RCTs, N=302, 12% vs. 6%, RR 2.19, 95% CI 0.77 to 5.39; I²=0%). We found moderate SOE for a large increased risk of dizziness (2 RCTs, 32% vs. 11%, RR 2.74, 95% CI 1.47 to 6.86, I2=0%). Extracted whole-plant products with high-THC to CBD ratios (oral) were associated with a large increased risk of study withdrawal due to adverse events (1 RCT, 13.9% vs. 5.7%, RR 3.12, 95% CI 1.54 to 6.33) and dizziness (1 RCT, 62.2% vs. 7.5%, RR 8.34, 95% CI 4.53 to 15.34). We observed a moderate improvement in pain severity when combining all studies of high-THC to CBD ratio (8 RCTs, N=684, MD −1.25, 95% CI −2.09 to −0.71, I2=50%; SOE: moderate). Evidence on whole-plant cannabis, topical CBD, low-THC to CBD, other cannabinoids, comparisons with active products, and impact on use of opioids was insufficient to draw conclusions. Other important harms (psychosis, cannabis use disorder, and cognitive effects) were not reported.

Conclusions. Low to moderate strength evidence suggests small to moderate improvements in pain (mostly neuropathic), and moderate to large increases in common adverse events (dizziness, sedation, nausea) and study withdrawal due to adverse events with high- and comparable THC to CBD ratio extracted cannabinoids and synthetic products in short-term treatment (1 to 6 months). Evidence for whole-plant cannabis, and other comparisons, outcomes, and PBCs were unavailable or insufficient to draw conclusions. Small sample sizes, lack of evidence for moderate and long-term use and other key outcomes, such as other adverse events and impact on use of opioids during treatment, indicate that more research is needed.

Objectives. Chronic pain is common, and opioid therapy is frequently prescribed for this condition. This report updates and expands on a prior Comparative Effectiveness Review on long-term (≥1 year) effectiveness and harms of opioid therapy for chronic pain, including evidence on shorter term (1 to 12 months) outcomes.

Data sources. A prior systematic review (searches through January 2014), electronic databases (Ovid MEDLINE®, Embase®, PsycINFO®, Cochrane CENTRAL, and Cochrane Database of Systematic Reviews through August 2019), reference lists, and clinical trials registries.

Review methods. Predefined criteria were used to select studies of patients with chronic pain prescribed opioids that addressed effectiveness or harms versus placebo, no opioid use, or nonopioid pharmacological therapies; different opioid dosing methods; or risk mitigation strategies. Effects were analyzed at short-term (1 to <6 months), intermediate-term (≥6 to <12 months), and long-term (≥12 months) followup. Studies on the accuracy of risk prediction instruments for predicting opioid use disorder or misuse were also included. Random effects meta-analysis was conducted on short-term trials of opioids versus placebo, opioids versus nonopioids, and opioids plus nonopioids versus an opioid or nonopioid alone. Magnitude of effects was classified as small, moderate, or large using predefined criteria, and strength of evidence was assessed.

Results. We included 115 randomized controlled trials (RCTs), 40 observational studies, and 7 studies of predictive accuracy; 134 were new to this update. Opioids were associated with small benefits versus placebo in short-term pain, function, and sleep quality. There was a small dose-dependent effect on pain, and effects were attenuated at longer (3 to 6 month) versus shorter (1 to 3 month) followup. Opioids were associated with increased risk of discontinuation due to adverse events, gastrointestinal adverse events, somnolence, dizziness, and pruritus versus placebo. In observational studies, opioids were associated with increased risk of an opioid abuse or dependence diagnosis, overdose, all-cause mortality, fractures, falls, and myocardial infarction versus no opioid use; there was evidence of a dose-dependent risk for all outcomes except fracture and falls.

There were no differences between opioids and nonopioid medications in pain, function, or other short-term outcomes. Opioid plus nonopioid combination therapy was associated with little improvement in pain at short-term followup versus an opioid alone. Co-prescription of benzodiazepines or gabapentinoids was associated with increased risk of overdose versus an opioid alone. No RCT evaluated intermediate- or long-term benefits of opioids versus placebo. One trial found stepped therapy starting with opioids to be associated with higher pain intensity and no difference in function or other outcomes versus stepped therapy starting with nonopioid therapy.

Limited evidence indicated no differences between long- and short-acting opioids in effectiveness, but long-acting opioids were associated with increased risk of overdose. One RCT found a taper support intervention associated with greater improvement in function but no difference in pain versus usual care.

Estimates of diagnostic accuracy for various risk prediction instruments were highly inconsistent, and there was no evidence on the effectiveness of risk mitigation strategies for improving clinical outcomes, with the exception of one study that found provision of naloxone associated with decreased emergency department visits.

Trials of patients with prescription opioid dependence found buprenorphine maintenance associated with better outcomes than buprenorphine taper and similar effects of methadone versus buprenorphine. Evidence was insufficient to evaluate benefits and harms of opioid therapy in patients at higher risk for opioid use disorder.

Conclusions. At short-term followup, for patients with chronic pain, opioids are associated with small beneficial effects versus placebo but are associated with increased risk of short-term harms and do not appear to be superior to nonopioid therapy. Evidence on intermediate-term and long-term benefits remains very limited, and additional evidence confirms an association between opioids and increased risk of serious harms that appears to be dose-dependent. Research is needed to develop accurate risk prediction instruments, determine effective risk mitigation strategies, clarify risks associated with co-prescribed medications, and identify optimal opioid tapering strategies.