Exploring Cerumen as an Alternative Matrix for Drug Detection and Quantification: Method Development and Application in Clinical Samples.

Cerumen (earwax) is a complex mix of apocrine and holocrine secretions and skin cells. In recent years, it has emerged as an innovative specimen for the detection of xenobiotics, suggesting that it has both clinical and forensic applications. An LC-MS/MS method was developed for the detection of 33 psychoactive medications in cerumen and urine and applied to samples from 60 psychiatric inpatient volunteers. The history of administration and qualitative results between urine and cerumen were generally consistent, with haloperidol, quetiapine, and nebivolol being detected more frequently in cerumen. In certain cases, drugs were detected both with very recent and without any recent administration, even when they were not in urine, highlighting opportunities for utilization in monitoring both acute and chronic administration and even following the cessation of administration. However, no clear relationship was found between drug concentrations and time of administration or total daily dose in most cases, consistent with challenges of routine collection. Cerumen concentrations were higher among more hydrophilic drugs with lower molecular weight and protein binding and demonstrated the best fit with an inverse regression model. No relationship was found with patient sex. Our results suggest that the disposition of drugs in cerumen is complex, being downstream of insufficiently elucidated pathways through migrating skin cells, ceruminous, and sebaceous glands. The present study is the first to investigate the routine collection of cerumen in a clinical setting and has broad implications for the interpretation of drug testing results with this emerging alternative biological specimen.