NEW YORK (Reuters Health)—Oral synthetic cannabis products that have a high tetrahydrocannabinol (THC) to cannabidiol (CBD) ratio, as well as extracted cannabis products with comparable THC-to-CBD ratios, may provide moderate, short-term improvements in chronic pain, a large systematic review of relevant research suggests.1
However, these products are also associated with higher risks for side effects, including sedation and dizziness, and few benefits in overall functioning, researchers report in Annals of Internal Medicine.
Chronic pain affects roughly 100 million Americans. Patients are increasingly turning to CBD products as an alternative to opioids and other pain medications.
In their review, researchers from Oregon Health & Science University in Portland evaluated the benefits and harms of cannabinoids to treat chronic pain, using a novel categorization scheme for the amount of THC versus CBD in cannabis products.
Their review included 18 randomized, placebo-controlled trials with 1,740 participants and seven cohort studies with more than 13,000 participants. The studies were primarily short, lasting one to six months, and more than half (56%) enrolled patients with neuropathic pain.
The data suggest that synthetic products with high THC-to-CBD ratios (>98% THC) may provide moderate improvement in pain severity and response (30% or more improvement) at the cost of an increased risk for sedation and dizziness.
Extracted products with high THC-to-CBD ratios (range, 3:1 to 47:1) may carry a “large” increased risk for study withdrawal due to side effects and dizziness, note Marian McDonagh, PharmD, and colleagues.
Sublingual spray with comparable THC-to-CBD ratio (1.1:1) “probably” is associated with small improvement in pain severity and overall function and may be associated with a large increased risk for dizziness and sedation and moderate increased risk for nausea, they found.
“Evidence for whole-plant products, CBD, and other cannabinoids was limited by serious imprecision and lack of ability to assess consistency and study methodological limitations,” the researchers write.
They also note that the studies did not evaluate harm outcomes and often excluded patients who were at higher risk for harms, “potentially underestimating the harms of cannabinoid treatment.”
Other key adverse-event outcomes—including psychosis, cannabis-use disorder and cognitive deficits—and outcomes on the effect on prescription-opioid use also were not reported or insufficient.
Overall, Dr. McDonagh and colleagues say the evidence base on cannabis-based products for chronic pain has “several important limitations that affect applicability of the findings and our ability to understand the effects of specific products in particular patients.”
