The Current Landscape of Medicinal Cannabis and Pharmacogenomics
Written by Nadim Gamarra PharmD ‘23
Published on May 4, 2021
There are few topics that can prompt controversial discussion as much as the legalization of marijuana. Nevertheless, the use of cannabis for medical purposes continues to advance. As of 2021, there are 36 states in the United States that have approved comprehensive, publicly available medical cannabis programs. For instance, in 2016 the governor of Pennsylvania signed Senate Bill 3, authorizing individuals with certain medical conditions to obtain and use medical marijuana. Some of the medical conditions covered by this bill include cancer, HIV/AIDS, Parkinson’s disease, multiple sclerosis, epilepsy, and inflammatory bowel disease.
Despite state legislature allowing the use of medical cannabis, federal law still classifies marijuana as an illicit, Schedule I drug. Therefore, research efforts to determine the place of cannabis in clinical practice are significantly hindered. With this being said, there are a few FDA-approved prescription medications derived from the marijuana plant. Epidiolex®, for example, is a purified CBD product indicated for seizures associated with Lennox-Gastaut syndrome or Dravet syndrome. In addition, Marinol® (synthetic THC) and Cesamet® (synthetic cannabinoid) are used to treat nausea and vomiting in chemotherapy patients.
Indeed, cannabis is a promising option for patients with inflammatory diseases, neurologic conditions, and chronic pain. Nevertheless, adverse events such as dry mouth, fatigue, somnolence, euphoria, and hallucinations can occur with its use. Because each patient metabolizes cannabis differently, the occurrence of any given side effect is difficult to predict. This is where pharmacogenomics comes into play. Using information about genes that affect cannabinoid distribution and metabolism, clinicians can recommend individualized regimens that prevent side effects and drug interactions.
The goal is to rely on results of pharmacogenomic testing rather than subjecting patients to trial-and-error treatment. This may lead to better relationships with patients, increased trust in the healthcare system, and cost reductions as therapy becomes streamlined and targeted.
A 2020 study on pharmacogenetic-guided cannabis use demonstrates the value of this model. Genomic data from 20 participants was evaluated to identify polymorphisms of CYP2C9, AKT1, and COMT (genes that play key roles in cannabis pharmacokinetics). It turns out that 25% of participants had genotypes that put them at high risk for cannabis-induced psychosis, and 10% had genotypes indicating high risk for cannabis-induced neurocognitive impairment. Pharmacists then provided counseling on the best strain and dose of cannabis to avoid these adverse effects. Seventy-five percent of the patients felt that these consultations added value to their health and wellbeing.
Of course, a crucial limiting factor is the availability of pharmacogenomic testing. In January of 2021, Genomid Inc. announced that its PGx Express test is covered and reimbursed by Medicare to support mental health patients. Hopefully, similar advancements will be made for medical cannabis in the coming years. In this series of blogs, I will be exploring the role of medical marijuana in the treatment of neurological diseases. More specifically, I would like to discuss how pharmacogenomics is changing this area of healthcare. Stay tuned because the era of personalized medicine is here!