There are a number of potential drug drug interactions with cannabis-based medicinal products and other medications or substances. Data suggests that CBD and THC act as enzyme inhibitors of cytochrome P-450 isoenzymes. Therefore caution should be taken when cannabis-based medicines are co-administered with any medications that are CYP inhibitors or inducers.

Cannabis-based medicinal products may also be susceptible to pharmacodynamic drug drug interactions. Clinicians should take into consideration the impact of cannabis based medicinal products on pharmacodynamics as doses of other medications may need to be adjusted.

Due to the lack of experience with cannabis-based medicinal products there may still be undiscovered drug drug interactions not stated in the tables above. Different cannabis-based medicinal products will contain varied concentrations of THC and CBD which may impact on the DDIs seen. It is recommended that any suspected adverse reaction is reported via the Yellow Card Scheme.

For information regarding potential adverse events with CBD oil a specific UKMi Q&A has been published: Cannabidiol oil – potential adverse effects