Hair Versus Nails: Is There a Place for Other Keratin Matrices?

The document discusses the growing interest in using nails, a keratinized matrix like hair, to evaluate long-term and retrospective exposure to drugs of abuse and other substances of toxicological interest. It highlights the differences between nails and hair that may affect drug incorporation and interpretation of results. The chapter provides an overview of the main characteristics of nails, the primary mechanisms of drug incorporation into nails, and methodologies for analyzing different drugs of abuse and psychoactive drugs in nails. It also evaluates the usefulness of nails for toxicological analysis by comparing the disposition and concentrations of different drugs in hair and nails after single-dose administration and in cases of chronic exposure. The document concludes with special considerations for interpreting nail result.