CBD is metabolized by the hepatic P450 set of enzymes. There can be interactions between CBD and pharmaceutical drugs, but it is rare that they are significant.
it is extremely common for patients to take two drugs at the same time that compete for this enzyme system, but despite this, there are not all that many problematic interactions and in particular, interactions between CBD and pharmaceuticals drugs is very rare.
The reason is explained in the following article:
So it seems, that at certain doses of CBD, in interaction with pharmaceutical drugs increases. It is interesting that with smoking THC, which many have done for many years, nobody ever worried about drug interactions. I think this is a positive trend as physicians are beginning to look at cannabis as real medicine with benefits as well as potential pharmaceutical drug interactions.
As stated in the above article, at high enough doses, it is quite possible to have CBD raise the levels of many medications using the P450 system. The issue is that clinically we just don’t see them or are not aware of them. Perhaps the reason is best explained by the above article. It states, that doses of whole plant CBD of 40mg or less, per dose, there is no noted competition with other drugs using the P450 system. So far, I have never recommended a single dose of whole plant CBD greater than 40mg.
So, we should continue to look and check patients pharmaceutical drug levels when available, but I just don’t think that at reasonable doses we need to worry much about it.