Metabolism, Not Mendacity: Rethinking Prolonged Cocaine Positivity

Urine toxicology is a cornerstone of monitoring abstinence in substance use disorder treatment, yet commonly cited detection windows are based on studies in healthy volunteers and do not account for metabolic variability. Prolonged metabolite positivity is typically interpreted as continued use, which can jeopardize treatment engagement and erode the therapeutic alliance.

We describe a 42-year-old man with severe stimulant use disorder whose urine toxicology remained positive for cocaine metabolites for 18 days, including 12 days after verified abstinence in a residential program. Laboratory evaluation revealed hepatic steatosis, and pharmacogenomic testing demonstrated a poor metabolizer phenotype at CYP2D6 and CYP3A5. Creatinine-corrected benzoylecgonine levels showed steady monotonic decline without fluctuation, consistent with delayed elimination rather than recurrent use. No cross-reactive medications or confounding substances were present.

Cocaine metabolism depends on cytochrome P450 enzymes-particularly CYP2D6 and CYP3A isoforms-and nonspecific esterases. Impaired activity of these pathways, combined with hepatic steatosis and chronic stimulant exposure, can significantly prolong metabolite clearance. This case highlights the importance of distinguishing biological variability from behavioral relapse, especially in settings where misinterpretation may undermine therapeutic rapport.

Unexpectedly persistent cocaine positivity should prompt consideration of pharmacogenomic variation, hepatic function, and confirmatory testing rather than immediate assumptions of relapse. Integrating biological, behavioral, and contextual data supports accurate interpretation and protects the therapeutic alliance.

Prolonged cocaine metabolite detection can reflect delayed metabolic clearance rather than continued use. Awareness of pharmacokinetic and pharmacogenomic factors is essential for accurate urine toxicology interpretation and patient-centered addiction care.