Cannabinoid-based medications for pain

Psychiatric disorders and CBM. The psychological impact of CBM use among patients enduring chronic pain can include sedation, cognitive/attention disturbance, and fatigue. These adverse effects can limit the utility of such agents.^22,29,45

Contraindications for CBM use, and conditions for which CBM ought to be used with caution, are listed in Table 3^54,55.The safety of CBM, particularly in patients with chronic pain and psychiatric disorders, has not been examined. Patients with psychiatric disorders may be poor candidates for medical cannabis. Epidemiologic data suggest that recreational cannabis use is positively associated both cross-sectionally and prospectively with psychotic spectrum disorders, depressive symptoms, and anxiety symptoms, including panic disorder.⁵⁶ Psychotic reactions have also been associated with CBM (dronabinol and nabilone).⁵⁷ Cannabis use also has been associated with an earlier onset of, and lower remission rates of, symptoms associated with bipolar disorder.^58,59 Consequently, patients who have been diagnosed with or are at risk for developing any of the aforementioned conditions may not be suitable candidates for CBM. If CBM are used, patients should be closely monitored for the emergence/exacerbation of psychiatric symptoms. The frequency and extent of follow-up is not clear, however. Because of its reduced propensity to produce psychoactive effects, CBD may be safer than THC for managing pain in individuals who have or are vulnerable to developing psychiatric disorders.

There is a lack of evidence to support the use of CBM for treating primary depressive disorders, general anxiety disorder, posttraumatic stress disorder, or psychosis.^60,61 Very low-quality evidence suggests that CBM could lead to a small improvement in anxiety among individuals with noncancer pain and MS.⁶⁰ However, interpreting causality is complicated. It is plausible that, for some patients, subjective improvement in pain severity may be related to reduced anxiety.⁶² Conversely, it is equally plausible that reductions in emotional distress may reduce the propensity to attend to, and thus magnify, pain severity. In the latter case, the indirect impact of reducing pain by modifying emotional distress can be impacted by the type and dose of CBM used. For example, low concentrations of THC produce anxiolytic effects, but high concentrations may be anxiety-provoking.^63,64

Several potential pharmacokinetic drug interactions may arise between herbal cannabis or CBM and other medications (Table 4^65,66). THC and CBD are both metabolized by cytochrome P450 (CYP) 2C19 and 3A4.^65,66 In addition, THC is also metabolized by CYP2C9. Medications that inhibit or induce these enzymes can increase or decrease the bioavailability of THC and CBD.⁶⁷

Simultaneously, cannabinoids can impact the bioavailability of co-prescribed medications (Table 5^66,68). Although such CYP enzyme interactions remain a theoretical possibility, it is uncertain whether significant perturbations in plasma concentrations (and clinical effects) have been encountered with prescription medications when co-administered with CBM.⁶⁹ Nonetheless, patients receiving CBM should be closely monitored for their response to prescribed medications.⁷⁰

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