One of the great things about legalizing marijuana is the amount of clinical data we are now able to garner about the plant.
Before legalization, while marijuana was commonly used to self medicate, it was rarely talked about. It was certainly not studied to the degree that we see now. Even with its wide spread use, we knew relatively little about its effects and particularly, how it would interact with other medications.
We now know that cannabis is an inhibitor of CYP 2C19 (27), an enzyme responsible for metabolizing many drugs, including two of the most widely used antidepressants: citalopram and escitalopram.
What does this mean for people using cannabis and also taking one of these medications?
Well, if cannabis inhibits the enzyme responsible for breaking down these drugs, that means that the drug will be broken down more slowly. With regular dosing, this could lead to a build up of the medication in the body. So the general plan with these interactions is to reduce the dose of the drug affected. Citalopram is usually dosed between 10 and 40mg per day, whereas escitalopram is usually dosed between 5 and 20mg per day. Indeed we see that the guidance from B.C.’s Provincial Academic Detailing is to reduce the maximum dose of citalopram and escitalopram by 50% (max dose of 20mg for citalopram and 10mg for escitalopram). This is a SIGNIFICANT dose decrease we are now suggesting to our patients that prior to legalization we never even knew to consider.
Key takeaway: tell your doctor and pharmacist if you are using cannabis products. It could affect the way you take your other medications. ***It is not advised to change doses of any medications without discussing with your prescriber first!***