Medical Marijuana and its Analgesic Potential in Pain

Written by Melissa Nguyen PharmD’19
Published on October 11, 2017

The dried leaves, stems, and flowers from a hemp plant named Cannabis sativa is infamously known as marijuana. Although it is commonly used for its psychoactive effects and recreational uses through smoking and consumption, it has gained attention for medical use. Tetrahydrocannabinol (THC) and cannabidiol (CBD) are marijuana’s active ingredients, and these are being researched as therapeutic options for some indications. Medical marijuana is not approved by the US Food and Drug Administration (FDA) for any medical indication.  While the FDA has not approved it for medical use and the Drug Enforcement Administration (DEA) deems marijuana as federally illegal to possess, its medical use has been legalized in some states. Regardless of legal approval, many believe in the medical use of marijuana for a variety of conditions.   This blog will present an overview of medical marijuana uses for two specific conditions:  neuropathic pain and cancer pain.

Marijuana may induce a “high” when smoked recreationally; however, it may also treat chronic neuropathic pain. Current therapy for neuropathic pain includes anticonvulsants, opioids, local anesthetics, and antidepressants. These however, are not always effective. A randomized, double-blind, placebo-controlled, crossover study by Wilseye et. al explored the analgesic efficacy of vaporized cannabis in patients. They compared two doses of vaporized cannabis to placebo for the treatment of neuropathic pain related to injury or disease of the spinal cord. Forty-two patients inhaled 4 puffs of vaporized cannabis containing either placebo, 2.9%, or 6.7% delta-9-THC on three separate occasions. Three hours later, they took a second dose where participants chose to inhale 4 to 8 puffs. The primary endpoint was dependent on an 11-point pain scale from 0 (no pain) to 10 (worst pain possible). Placebo demonstrated the least amount of pain reduction, while the first and second doses of cannabis “pain intensity” reduction was significantly lower (P<0.1) by 1 at 420 minutes. This “pain intensity reduction” at 420 minutes, was only statistically significant compared to placebo, and not between 2.9% and 6.7% delta-9-THC.

Despite its efficacy, the lower and higher doses of delta 9-THC were comparable to each other. The results were mixed since the number needed to treat (NTT) analgesic effect for a 30% pain reduction during an 8 hours period when comparing the higher and lower doses to placebo were not statistically different. In fact, the NTT for the lower dose when compared to placebo was 4, whereas the NTT for the higher dose in comparison to placebo was 3. The NTTs for delta 9-THC were calculated with a 95% CI and the authors presented these data in a confusing fashion.  However, one may infer that delta 9-THC may have a ceiling effect and that these NTTs were also similar to the NTT of current standards of care such as pregabalin (3.9) and gabapentin (3.8). Despite its limitation, delta 9-THC reduced pain compared to placebo illustrating its potential for treating neuropathic pain.

Marijuana has also been considered an option in reducing cancer pain. To further explore marijuana’s use in cancer pain, a review by Chistewek looked at different therapeutic options. Cancer pain is usually treated in an accordance with the World Health Organization ladder and often with an opioid, a non-opioid, and an adjuvant. Chistewek evaluated different sources for the use of canniboids in cancer pain which illustrate a mixed effect. While marijuana induces analgesia for acute and chronic pain, it only has moderate evidence to support its use in chronic pain. Not much evidence exists for cancer pain, because not many trials evaluated medical marijuana for this specific disease. A marijuana derived medication, a cannaboid Nabiximols (Sativex®), is an oralmucosal spray has shown effectiveness in cancer pain.  It consists of a 50:50 mixture of THC and CBD, but its efficacy is limited due to a dose ceiling effect. Despite its limitation, in Canada it may be used to treat cancer pain refractory to opioids. In the United States, the FDA has fast-tracked its evaluation for its use in cancer pain in 2014. The limited findings in current publications portray more research needs to be done to show its efficacy and use in cancer pain.

While many use marijuana recreationally, its medical potential cannot be denied. Marijuana’s therapeutic use is not limited to cancer or neuropathic pain. Current findings are limited because of its federal restrictions, yet it is continuously being researched as an option for many indications such as multiple sclerosis. post-traumatic stress disorder, and seizures. In the future, the US government may no longer label marijuana as a Schedule I drug, forging the path for more research and FDA approved medical uses.

Categories:  Department of Health Policy and Public HealthPublic HealthStudentsMayes College of Healthcare and Business PolicyDepartment of Pharmaceutical and Healthcare BusinessMarijuanaHealth PolicySubstance Use Disorders Institute