Mohamed and colleagues followed 33 patients using cannabinoid preparations for neurological care. Sixteen used an oromucosal spray and 17 used oil-based preparations. The investigators measured plasma THC and CBD immediately before the morning dose and again 2.5 hours after dosing. For 45% of patients, both trough results were at or below the 0.1 ng/mL limit of detection.
The trough result describes the sampled plasma at that point in the dosing interval. The study also found increases in cannabinoid concentrations after dosing in patients using two of the preparations. A low morning value can therefore be consistent with ongoing treatment and higher concentrations at another time. This interpretation depends on the assay’s detection limit, the specimen type and the timing of the draw.
Obtain the dosing and collection times, product information and the laboratory’s reporting limits. The two study draws provide a snapshot of change. They do not establish each patient’s maximum concentration or the concentration at a separate event. An inference about exposure earlier in the interval would need additional information.