Higher Cannabinoid Plasma Levels Often Accompanied Less Improvement in the Parkinson Trial
The Parkinson trial did not show a simple pattern of higher cannabinoid exposure producing greater benefit. Exploratory plasma correlations often ran in the opposite direction.
The concentration findings were exploratory
Plasma cannabinoid levels varied widely within the treated group. Higher levels correlated with less improvement on several assessments, including pain, depression, perceived sleep, anxiety and tremor amplitude. A different association favored improvement in bladder function.
Correlation did not randomize exposure
Participants were randomized to treatment, not to every measured plasma concentration. Achieved levels could reflect dosing, metabolism, tolerability and other differences. The correlations therefore do not establish that raising concentration caused worsening, or that lowering it would produce a predictable benefit.
No therapeutic concentration rule emerged
The main motor comparison was nonsignificant, and many exploratory outcomes were examined without adjustment across all different variables. These limitations prevent a reliable individualized concentration target from being derived. The findings are still useful because they challenge the assumption that more measured drug necessarily means more clinical improvement. State the analyte, sampling context and specific clinical outcome rather than converting a plasma value into a general score for benefit, toxicity or functional capacity.
Related analysis: the study’s broader findings and limitations.
