Pharmacovigilance in the Age of Legalized Cannabis: Using Social Media to Monitor Drug–Drug Interactions Between Immunosuppressants and Cannabis-Derived Products

Introduction A clinical trial of Epidiolex®, the only US FDA-approved cannabis-derived consumer product (CDP), discovered an interaction with an immunosuppressant (tacrolimus) that led to drug toxicity, highlighting the unique intersection of prescription and commonly unregulated consumer products. Objective We aimed to identify if similar drug–drug interactions (DDIs) are occurring among the consumer CDP market, even though they cannot be identified through trials. Methods We searched Reddit for subreddits related to CDPs or health, resulting in 63,561,233 posts. From these, we identified 190 posts discussing both immunosuppressants and CDPs. Two blinded investigators evaluated the following. (1) Was there a concern about a potential DDI between consumer CDPs and immunosuppressants? (2) Was there a unique adverse event attributed to a DDI between consumer CDPs and immunosuppressants? Results Of these, 66 posts (35%) expressed concern about a potential DDI, such as “Hey, my partner wants to try my edibles … she’s on Prograf [tacrolimus] and wants to talk to a stoner who’s had a heart transplant.” Four posts (2%) reported a unique DDI, such as “I have clinical results that are semi-anecdotal, showing the coordination to my halting substance use … It's the CBD. Shot my prograf to 30 at like 4 mg.” Two of the four reported DDIs are similar to those first reported for Epidiolex. The remaining two reported DDIs include a potential cannabidiol (CBD)/sirolimus or delta-9-tetrahydrocannabinol (THC)/sirolimus interaction and a THC/tacrolimus interaction, both resulting in drug toxicity. Conclusion This case study is the first to report on DDIs involving consumer CDPs, including both CBD and THC products, as well as a broader class of immunosuppressants. This demonstrates the risks associated with using consumer CDPs alongside prescription medications while highlighting the need for development of increased surveillance to monitor consumer CDPs for drug safety signals, as well as comprehensive regulations that take into account the unique characteristics of the consumer marketplace.