SOFT/TIAFT 98 - Localization of Drugs and Metabolites in Human Hair

SOFT - TIAFT 1998

Scientific Session 5

Thursday October 8, 1998

LOCALIZATION OF DRUGS AND METABOLITES IN HUMAN HAIR
	Kathryn S. Kalasinsky, Keith L. Egli and Alison F. Grieshaber Office of the Armed Forces Medical Examiner, Division of Forensic Toxicology, Armed Forces Institute of Pathology, Washington, DC 20306-6000, USA

Localization of drugs and metabolites in human hair is important in determining the pharmacokinetics of drug incorporation in hair. This information is critical to validate drug testing from hair. Infrared microscopy investigation of laterally microtomed hair has shown to be a valuable tool for imaging this drug distribution. Three dimensional contour maps of drug location are available of the hairs that have been probed by infrared microscopy. Studies have shown that hydrophobic drugs tend to bind to the central core or medulla of the hair while hydrophilic drugs tend to distribute throughout the hair and appear, generally, in lower concentrations per dose. The high spatial resolution available with current infrared microscopy instrumentation allows microprobing of the hair with finite location of the drug distribution within the hair.

Separation of the medullated hair segments from the non-medullated with subsequent GC/MS quantitation have shown that the medulla does play an interactive part in the drug binding in hair. Our studies with aged individuals with both pigmented and non-pigmented hair have shown that the drug is associated with the medullated portion of the non-pigmented hairs and both the medullated and non-medullated portions of the pigmented hair. This is evidence for a medulla binding as well as binding associated with the pigment of the hair. Microtoming a drug free hair and exposing the center portion to a drug/saline solution shows, by infrared microscopy, a preferential migration of the drug to the medulla of the hair. The infrared microscopic data is not quantitatable but can yield relative concentrations which are confirmed by GC/MS results.

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