Domain 2: How to introduce cannabinoids in patients with chronic pain taking opioids
The second domain asked questions regarding how to administer, initiate, titrate, and dose cannabinoids in the presence of opioids. The key consensus findings are:
1) There was consensus that the preferred format of administering cannabinoids was the oral route, using oil extracts or capsules. Sublingual tinctures may also be considered. There was consensus strongly recommending against smoking cannabis. Caution should be used in jurisdictions where regulated and standardized medical cannabis products are unavailable.
2) In the daytime, it was agreed that a patient should initiate with CBD oral dosing at a range of 5–20 mg. For THC, there was consensus that the initial THC dose range should be 0.5–3 mg and then titrated up by 1–2 mg every one or two weeks to reach chronic pain goals.
This initiation and titration protocol deserves further discussion. Cannabidiol was recommended as the initiating cannabinoid for daytime dosing partly because there is limited sedation or intoxication associated with CBD. 53 In addition, CBD unaccompanied by THC has been observed to support opioid tapering and reduce cue-induced cravings for opioids.54,55 Published CBD doses range from tens of mg to thousands of mg yet from a practical standpoint, the cost of CBD may become a limitation at high doses. As such there was no consensus on how high up the CBD dose should be titrated. It is important to note that the available evidence for CBD alone to improve chronic pain control is weak.56–59Preliminary studies examining topical application of CBD have observed that this route may be efficacious for treating pain, although further research is required.60,61
In contrast to CBD, the available evidence for THC to improve chronic pain control is relatively strong.7,62 During the consensus summit, it was noted that some patients can reach pain control goals with CBD alone, but it was quickly pointed out that many CBD preparations, both medical and recreational, contain a small percentage of THC and thus it could be the low concentration of THC providing the pain relief associated with CBD, especially at high CBD doses. Health care professionals may consider adding THC soon after CBD initiation if the patient is not reaching their chronic pain control goals.
The initiating dose range of 0.5–3mg THC was chosen based on clinical observations that patients typically begin to experience psychoactive effects at 2–2.5mg of THC, which is similar to the reported effective dose of dronabinol, a synthetic isomer of THC,63 and many patients would prefer to avoid the psychoactive effect. In addition, there is individual variability regarding the response to THC, and taking a “start low and go slow” approach is recommended. There are also reported sex differences in the response to THC as a recent placebo-controlled study observed that women experience similar psychoactive effects at a lower THC dose in comparison to men.64 Our consensus findings on how to initiate and titrate cannabinoids in the presence of opioids are similar to a previously published editorial on cannabinoid dosing for chronic pain management.65
A caveat to the “start low and go slow” approach may be considered with a patient at high risk for opioid-related harm. The need to rapidly increase cannabinoids may be apparent as the opioid taper may need to be more aggressive. Therefore, under certain circumstances, it may be appropriate to start low but go fast with cannabinoid introduction and titration. Patient-specific factors such as response and access to close monitoring may allow for a more aggressive cannabinoid titration and be a valuable strategy in a patient where the opioid risks are high.
3) For night-time use, there was no consensus on the CBD or THC dose, or the THC:CBD distribution ratio, although there was discussion around the potential importance of THC for sleep quality, which may support chronic pain relief.66
4) For breakthrough pain, vapourization of dried cannabis flower was recommended. It is important to note that vapourizing dried flower differs from vaping through an electronic cigarette device. Vapourization of dried flower is ideally accomplished with an approved medical devices, although many different types of vapourizers of differing quality could be used.67 In contrast, vaping cannabis using electronic cigarette devices may expose the patient to unsafe additives and increase the risk of a novel lung disease, EVALI (e-cigarette or vaping product use associated lung injury).68,69 Until such a time that electronic cigarette devices are proven safe, inhalation of medical cannabis for breakthrough pain should be undertaken exclusively with medically-approved vapourizers using dried cannabis flowers.