A patient evaluated for apparent alcohol withdrawal had a bupropion concentration of 133 ng/mL and a hydroxybupropion result reported as greater than 3,000 ng/mL. The two measurements tell different parts of the toxicology story.
The parent drug was below the reporting laboratory’s toxic threshold. The metabolite exceeded its own threshold and the assay’s upper reporting limit. The laboratory could report that the metabolite was above 3,000 ng/mL, but that result does not establish the exact concentration.
The patient’s prescription was for an extended-release formulation. The authors considered sampling time, ongoing absorption, and metabolism when interpreting the difference. In a case review, compare each analyte with its own reporting range and relate both results to the collection time before drawing conclusions about the presentation.