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An Exploratory Human Laboratory Experiment Evaluating Vaporized Cannabis in the Treatment of Neuropathic Pain From Spinal Cord Injury and Disease

  • Barth Wilsey
    Correspondence
    Address reprint requests to Barth Wilsey, MD, University of California Center for Medicinal Cannabis Research, Department of Psychiatry, University of California, San Diego, 220 Dickinson Street, Suite B, San Diego, CA 92103-8231.
    Affiliations
    VA Northern California Health Care System, Sacramento VA Medical Center, Mather, California

    Department of Physical Medicine and Rehabilitation, University of California, Davis Medical Center, Lawrence J. Ellison Ambulatory Care Center, Sacramento, California
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  • Thomas D. Marcotte
    Affiliations
    Department of Psychiatry, University of California, San Diego, San Diego, California
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  • Reena Deutsch
    Affiliations
    Department of Psychiatry, University of California, San Diego, San Diego, California
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  • Holly Zhao
    Affiliations
    VA Northern California Health Care System, Sacramento VA Medical Center, Mather, California

    Department of Physical Medicine and Rehabilitation, University of California, Davis Medical Center, Lawrence J. Ellison Ambulatory Care Center, Sacramento, California
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  • Hannah Prasad
    Affiliations
    VA Northern California Health Care System, Sacramento VA Medical Center, Mather, California

    Department of Physical Medicine and Rehabilitation, University of California, Davis Medical Center, Lawrence J. Ellison Ambulatory Care Center, Sacramento, California
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  • Amy Phan
    Affiliations
    VA Northern California Health Care System, Sacramento VA Medical Center, Mather, California

    Department of Physical Medicine and Rehabilitation, University of California, Davis Medical Center, Lawrence J. Ellison Ambulatory Care Center, Sacramento, California
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      Highlights

      • All Neuropathic Pain Scale descriptors were improved by vaporized cannabis.
      • There was significantly more pain relief with active cannabis than with placebo.
      • The two active doses did not significantly differ from each other in terms of analgesic potency.
      • Many of the psychoactive side effects were delta 9-THC concentration-dependent.

      Abstract

      Using 8-hour human laboratory experiments, we evaluated the analgesic efficacy of vaporized cannabis in patients with neuropathic pain related to injury or disease of the spinal cord, most of whom were experiencing pain despite traditional treatment. After obtaining baseline data, 42 participants underwent a standardized procedure for inhaling 4 puffs of vaporized cannabis containing either placebo, 2.9%, or 6.7% delta 9-THC on 3 separate occasions. A second dosing occurred 3 hours later; participants chose to inhale 4 to 8 puffs. This flexible dosing was used to attempt to reduce the placebo effect. Using an 11-point numerical pain intensity rating scale as the primary outcome, a mixed effects linear regression model showed a significant analgesic response for vaporized cannabis. When subjective and psychoactive side effects (eg, good drug effect, feeling high, etc) were added as covariates to the model, the reduction in pain intensity remained significant above and beyond any effect of these measures (all P < .0004). Psychoactive and subjective effects were dose-dependent. Measurement of neuropsychological performance proved challenging because of various disabilities in the population studied. Because the 2 active doses did not significantly differ from each other in terms of analgesic potency, the lower dose appears to offer the best risk-benefit ratio in patients with neuropathic pain associated with injury or disease of the spinal cord.

      Perspective

      A crossover, randomized, placebo-controlled human laboratory experiment involving administration of vaporized cannabis was performed in patients with neuropathic pain related to spinal cord injury and disease. This study supports consideration of future research that would include longer duration studies over weeks to months to evaluate the efficacy of medicinal cannabis in patients with central neuropathic pain.

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