Reddit posts revealed unreported drug interactions between cannabis products and immunosuppressants

What the researchers found

Searching 63.5 million Reddit posts, researchers identified 190 posts discussing both cannabis-derived products (CDPs) and immunosuppressants. Of these, 66 posts (35%) expressed concern about potential drug-drug interactions, and 4 posts (2%) reported actual adverse interactions. Two of the four matched the known CBD/tacrolimus interaction discovered in Epidiolex trials. Two others reported previously undocumented interactions: a CBD or THC/sirolimus interaction and a THC/tacrolimus interaction, both resulting in drug toxicity.

Why it matters

Consumer cannabis products are unregulated and cannot be tested in clinical trials the way Epidiolex was. This study demonstrates that real-world drug interactions are occurring with consumer CBD and THC products and going unreported to formal pharmacovigilance systems, creating a hidden safety gap.

The numbers in context

63.5 million Reddit posts searched; 190 relevant posts identified; 66 (35%) expressed DDI concern; 4 (2%) reported actual DDI events; 2 novel interactions discovered: CBD/THC with sirolimus and THC with tacrolimus

How the study worked

Searched Reddit for subreddits related to cannabis-derived products or health, yielding 63,561,233 posts. Identified 190 posts discussing both immunosuppressants and CDPs. Two blinded investigators evaluated posts for DDI concerns and reported adverse events.

What this study cannot tell us

Social media data cannot verify clinical outcomes or confirm causation. Four reported DDI events is a very small number from which to draw conclusions. Reddit users may not accurately describe medications, doses, or outcomes. Cannot estimate the true incidence of these interactions.

How to read the evidence

Novel pharmacovigilance methodology identifies real safety signals, but social media data cannot verify clinical outcomes or establish interaction mechanisms.

When this study was published

2025 publication

The bigger picture

As cannabis legalization expands while millions of Americans take immunosuppressants for organ transplants, autoimmune diseases, and cancer, the interaction risk grows. Traditional pharmacovigilance misses these events because consumer cannabis products exist outside the regulated pharmaceutical system.

Questions still open

• How many immunosuppressant patients use consumer cannabis products without informing their physicians? Should pharmacovigilance systems formally monitor social media for cannabis-drug interactions?

Common questions

Read the original research

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

Drug safety, 48(1), 99-105

Citation

Allen, Matthew R; Wightman, Gwenyth Portillo; Zhu, Zechariah; Poliak, Adam; Smith, Davey M; Dredze, Mark; Ayers, John W. (2025). Pharmacovigilance in the Age of Legalized Cannabis: Using Social Media to Monitor Drug-Drug Interactions Between Immunosuppressants and Cannabis-Derived Products.. Drug safety, 48(1), 99-105. https://doi.org/10.1007/s40264-024-01481-x

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