The high lipid-solubility of cannabinoids results in their persisting in the body for long periods of time.[131] Even after a single administration of THC, detectable levels of THC can be found in the body for weeks or longer (depending on the amount administered and the sensitivity of the assessment method).[131] A number of investigators have suggested that this is an important factor in marijuana's effects, perhaps because cannabinoids may accumulate in the body, particularly in the lipid membranes of neurons.[132]

Did you get an answer for this? I have the exact same scenario. I'm treating my TN with Tegretol, and recently tried CBD. I think I took too much and there are some weird drug interactions with Tegretol and I felt quite stoned....was alone and talking to myself in my head thinking I was Einstein. It freaked me out a bit but I think I took too much. I'm trying lower doses again as recently my TN seems to be resisting the meds, although I have had a lot of emotional stress, which seems to be a trigger. Thanks!! Anna