Guideline Weakly Supports Trying Cannabinoids for Chronic Pain

Liz Scherer

September 21, 2021

"Evidence alone is not sufficient for clinical decision-making, particularly in chronic pain," said Jason Busse, DC, PhD, director of Michael G. DeGroote Centre for Medicinal Cannabis Research at McMaster University, Hamilton, Ont., and lead author of a newly released rapid guideline on medical cannabis or cannabinoids for chronic pain.

Dr Jason Busse

The recommendations, published online Sept. 9, 2021 in the British Medical Journal, suggest that providers offer patients with chronic pain a trial of noninhaled medical cannabis or cannabinoids if standard care or management is ineffective. However, the "weak" rating attached to the recommendation may compel some clinicians to automatically write off the panel's recommendations.

"Because of the close balance between benefits and harms and wide variability in patient attitudes, the panel came to the conclusion that [some] patients presented with the current best evidence would likely choose to engage in a trial of medicinal cannabis, if their current care was felt to be suboptimal," Busse explained in an interview.

But more importantly, "the recommendation allows for shared decision making to occur, and for different patients to make different decisions based on individual preferences and circumstances," he said.

Evidence Supports Improved Pain and Sleep Quality, Physical Functioning

Evidence supporting the use of medical cannabis in chronic pain is derived from a rigorous systematic review and meta-analysis of 32 studies enrolling 5,174 patients randomized to oral (capsule, spray, sublingual drops) or topical (transdermal cream) medical cannabis or placebo. Of note, three types of cannabinoids were represented: phytocannabinoids, synthetic, and endocannabinoids.

The studies included both patients with chronic noncancer pain (28 studies, n = 3,812) and chronic cancer pain not receiving palliative care (4 studies, n = 1,362). On average, baseline pain scores were a median 6.28 cm on a 10-cm visual analog scale (VAS), and median participant age was 53 years. 60% of trials reporting sex differences enrolled female participants. Overall, patients were followed for roughly 2 months (median, 50 days).

Findings (27 studies, n = 3,939) showed that, compared with placebo, medical cannabis resulted in a small, albeit important, improvement in the proportion of patients experiencing pain relief at or above the minimally important difference (MID) (moderate-certainty evidence, 10% modeled risk difference [RD; 95% confidence interval, 5%-15%] for achieving at least the MID of 1 cm).

Medical cannabis (15 studies, n = 2,425) also provided a small increase in the proportion of patients experiencing improvements in physical functioning at or above the MID (high certainty evidence, 4% modeled RD [95% CI, 0.1%-8%] for achieving at least a MID of 10 points).

Additionally, participants experienced significant improvements in sleep quality, compared with placebo (16 studies, 3,124 participants, high-quality evidence), demonstrating a weighted mean difference of –0.53 cm on a 10-cm VAS (95% CI, –0.75 to –0.30 cm). A total of nine larger trials (n = 2,652, high-certainty evidence) saw a small increase in the proportion of patients experiencing improved sleep quality at or above the MID: 6% modeled RD (95% CI, 2%-9%).

On the other hand, benefits did not extend to emotional, role, or social functioning (high-certainty evidence).

First Do No Harm: Start Low, Go Slow

While these findings provide a rationale for medical cannabis in chronic pain, exploring options with patients can be challenging. Studies on medical cannabis consistently note that patients want information, but data also show that many providers express a lack of knowledge to provide adequate counseling.

There are also legal hurdles. Despite the authorization of medicinal cannabis across a majority of states and territories, cannabis is still a schedule I substance under the Federal Controlled Substances Act. In addition, the absence of standards around formulations, potency, and dosing has also been cited as a major barrier to recommending medical cannabis, as have concerns about adverse events (AEs), especially with inhaled and tetrahydrocannabinol (THC)-predominant formulations.

Like most medications, medical cannabis dosing should be individualized depending on product, patient, and ability to titrate the dose, but the guidelines provide a general rule of thumb. Providers considering therapeutic noninhaled medical cannabis trials are encouraged to start with a low-dose cannabidiol (CBD) oral tablet, spray, or sublingual oil drops 5 mg twice daily, increasing it by 10 mg every 2-3 days depending on the clinical response (to a maximum daily dose of 40 mg/day). If patient response is unsatisfactory, they should consider adding 1-2.5 mg THC/daily, titrated every 2-7 days to a maximum of 40 mg/day.

Still, an important caveat is whether or not adjunctive CBD alone is effective for chronic pain.

Dr Ziva Cooper

"While we know that one out of seven U.S. adults are using cannabidiol, we know very little about its therapeutic effects when given by itself for pain," Ziva Cooper, PhD, director of the Cannabis Research Initiative at the University of California, Los Angeles, and an associate professor at-large of psychology and behavioral science, said in an interview. (Cooper was not involved in the guideline development.)

"But patients tend to self-report that CBD is helpful, and at low doses, we know that it is unlikely to have adverse effects of any significant concern," Cooper noted.

Depending on its components, medical cannabis is associated with a wide range of AEs. Studies comprising the evidence base for the guideline reported transient cognitive impairment (relative risk, 2.39; 95% CI, 1.06-5.38), vomiting (RR, 1.46; 95% CI, 1.07-1.99), and drowsiness (RR, 2.14; 95% CI, 1.55-2.95), attention impairment (RR, 4.04; 95% CI, 1.67-9.74), and nausea (RR, 1.59; 95% CI, 1.28-1.99). Of note, findings of a subgroup analysis showed that the risk of dizziness increased with treatment duration, starting at 3 months (test of interaction P = .002).

However, Cooper explained that, because the included studies were inconsistent in terms of cannabis type (e.g., some looked at synthetic THC or THC-like substances where others looked at a THC/CBD combination) and formulation (capsules, oral mucosal sprays), it's difficult to tease out component-specific AEs.

"These are really important things to note, especially when you think about different populations that might be using these types of medicines moving forward," she said.

Toward that end, the guideline specifically states that there is "no reason why the expected benefits would be systematically different among adolescents and emerging adults."

Among children with cancer, prior study findings reinforce the conclusion that benefits are similar to adults, but studies in this area are limited to end-of-life treatment, childhood cancer with primarily palliative intent, or progressive or relapsed cancer. Because THC's safety profile is less certain in children, it's also important to consider adverse neurocognitive effects before initiating a medical cannabis trial in this population.

Navigating the Landscape

Although promising, the medical cannabis landscape is undoubtedly difficult to navigate, with land mines ranging from a limited inability to simply pick up a prescribing pad to quality control.

With the exception of three Food and Drug Administration–approved products – dronabinol, cannabidiol Rx, and nabilone – U.S. providers are only able to 'certify,' not prescribe, medical cannabis for chronic pain, and only if it is included within the state cannabis board's list of eligible conditions. (A state-by-state guide is available.)

Dr Jenny Wilkerson

Quality control also varies by product but is critical. "You want to look for certificates of quality assurance," Jenny Wilkerson, PhD, a research assistant professor of pharmacodynamics at the University of Florida, Gainesville, said in an interview. (Wilkerson was not involved in the guideline development.)

"A good dispensary should have that information or at least be willing to get that information, but generally speaking, that is something that patients need to ask for," she emphasized, noting that "most available mass readouts are not divided by lots."

Initial counseling and AE monitoring and regular follow-up is important, especially among patients who've never tried medical cannabis (or older patients whose prior experience may be limited to weaker recreational marijuana).

Notably, the reliance on medical dispensaries to deliver the right information at the right time may prove to be faulty. While recent data show that frontline dispensary workers regularly provide information to customers on their medical conditions and available products, they rarely, if ever, base recommendations on provider input, and never or rarely discuss potential AEs and other risks.

Per the new guideline, inexperienced patients should be seen monthly until a stable dose is achieved; longer times between visits can be considered in those who are more experienced. Still, patients should be advised to contact their provider when pain relief or other goals are insufficient, or when response or problematic AEs occur. This facilitates down-titration to a previously tolerated dose, up-titration in CBD and/or THC, or a different route of administration/formulation altogether.

Wilkerson pointed out that follow-up visits also provide an opportunity to do a blood draw and ask the lab to conduct pharmacokinetic analysis.

If possible, "ask patients to [ensure that they] take a standard dose before the visit so that the lab can assess the blood percentage of primary compounds and metabolites in the product that they are using," she explained, noting that the information is helping to determine how "the different ratios may be affecting therapeutic response in individual patients."

Granted, the guideline is only a start. But it is a good one.

"A lot of physicians want to be able to hang their hat on evidence of the safety and efficacy of these products, and the analysis that was leveraged for this guideline was very rigorous," Cooper said.

Not only do they reinforce that "oral cannabinoids can produce small improvements in pain and provide a dosing structure that minimizes risk to the patient, [but they] should be able to help educate physicians who [are looking] for a sense of what the literature tells us at this time," she added.

"With chronic pain, we often find that different treatments will show small potential benefits and they have a certain risk profile," Busse said.

"It's almost impossible to know what patients think about this option unless you present them with the evidence and ask them to make a decision based on their values and preferences," he said.

The Michael G. DeGroote Centre for Medicinal Cannabis Research funded the MAGIC Evidence Ecosystem Foundation to support the creation of the guideline. The center receives no funding from industry Busse, Cooper, and Wilkerson reported having no relevant financial relationships.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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