A low parent-drug result need not capture the entire active exposure.
A mexazolam review described metabolism to active products, including chloronordiazepam and chloroxazepam, and summarized anxiety-treatment studies. The pharmacokinetic discussion included extensive protein binding and metabolite elimination.
The review assembled heterogeneous evidence, and some underlying studies were small or early. It cannot establish an individual impairment threshold or generalize tolerability findings to every co-exposure.
Check which parent and metabolite compounds the laboratory method actually measures. Collection timing and metabolism can affect the pattern. A report should not equate a missing parent result with absence of pharmacological activity or infer a precise dose and performance level from a metabolite concentration alone.
Source: PMC4381915, supplied full-text paper. Findings are paraphrased; case-review implications are an interpretation.
Related: Forensic Toxicology: expert analysis and case review.