If you use marijuana (cannabis), be aware that it can interact with many medications, as outlined in a brief article in the Canadian journal CMAJ. For example, certain drugs can increase concentrations of tetrahydrocannabinol (THC) and cannabidiol (CBD), the active cannabinoids in cannabis, thereby boosting the drugs’ effects; these include the antifungal drug ketoconazole as well as some antibiotics, antidepressants, and medications for high blood pressure or arrhythmias.
Conversely, cannabinoids can increase levels of some medications, including the anti-clotting drug warfarin. Combining cannabis with other drugs that affect the central nervous system can create additive effects, resulting in, for instance, racing heartbeat and elevated blood pressure (when combined with stimulants) or drowsiness and impaired coordination (when combined with depressants like alcohol or opioids).
Some interactions between cannabis and medications can be serious. But there still hasn’t been much research in this area, and cannabis may also affect drugs other than those listed here. This chart shows known and possible interactions between cannabis and a variety of medications.
