Review Investigates Adverse Effects of Cannabidiol


According to a recent review published in the journal Current Neuropharmacology, the use of cannabidiol (CBD), the non-intoxicating component of cannabis, has been associated with numerous adverse effects based on available evidence from animal and human studies.

In their review, the study authors noted that while CBD use has become increasingly popular as an alternative therapy for a wide range of conditions, the evidence for its effectiveness for these unapproved uses is lacking. To identify adverse effects related to CBD use, the authors searched PubMed, Cochrane Central, and EMBASE from inception to January 2019 for studies where adverse effects or toxicity were reported. “Studies defining CBD’s beneficial effects were included to provide balance in estimating risk/benefit,” the authors explained.

In human studies, adverse effects included diarrhea, fatigue, vomiting, and somnolence, in addition to liver abnormalities. Moreover, in studies involving patients with epilepsy and psychiatric disorders, CBD was observed to affect several CYP450 enzymes including CYP2C8, CYP2C9, CYP1A2, and CYP2B6, all of which could potentially lead to CBD-induced drug interactions.

In animal studies, serious adverse effects such as embryo-fetal toxicity, spermatogenesis reduction, and neurotoxicity were also noted. However, doses administered in these studies were higher than those used in human trials.

Based on their findings, the authors concluded that if physicians continue to recommend CBD for off-label uses, the potential for adverse effects and drug interactions need to be taken into consideration as it is “not risk-free”.

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To date, only 1 cannabis-derived product (Epidiolex) and 3 cannabis-related products (Cesamet, Marinol, Syndros) have been approved by the Food and Drug Administration (FDA), however several companies have attempted to manufacture unapproved cannabidiol-related products.

In a perspective piece discussing the FDA’s current policy on CBD, Lowell Schiller, JD, Principal Associate Commissioner for Policy, writes “While we recognize the potential benefits of CBD, questions remain regarding its safety. The FDA is exploring potential pathways for various types of CBD products to be lawfully marketed. An important component of this work is obtaining and evaluating information to address outstanding questions related to the safety of CBD products that will inform the Agency’s consideration of potential regulatory frameworks for CBD while maintaining the FDA’s rigorous public health standards.”

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