Cannabinoids are molecules that have low toxicity and, therefore, safe to handle when correctly formulated from the therapeutic point of view. However, when the patient is taking other medications, care must be taken so that drug interactions do not occur, which may affect the patient.
Some cannabinoids have been observed to inhibit some liver enzymes and alter the metabolism of some medications. Caution should be exercised when taking these medications and advise the treating physician who is formulating medical cannabis: coumarins (anticoagulant), statins (for cholesterol and triglycerides), beta-blockers (for high blood pressure and the heart) and corticosteroids (for rheumatic diseases); itraconazole, fluconazole (for fungi), ritonavir (HIV), rifampin, clarithromycin (antibiotic); carbamazepine, phenytoin, phenobarbital, oxapapan (anticonvulsants), St. John's wort (Tranquilizer).
If you are a woman and are taking contraceptives, you should also inform your doctor, because cannabinoids can decrease the effect.