ABSTRACT
This chapter describes a series of effects concentrating on physicochemical factors that influence drug incorporation and drug behavior in the hair and the hair root based on our studies utilizing this isolation of the vascular contribution. To determine the effect of functional groups on incorporation rates (ICR), the ICR of 32 phenethylamines having the same skeleton but a series of different functional groups were compared with each other. It is presumed that three main physicochemical properties—melanin affinity, lipophilicity, and basicity—are hypothesized as affecting drug incorporation into hair. To examine this hypothesis, these main physicochemical properties were compared to the ICR of various drugs to see if identifiable patterns are present in the ICR that vary according to one or more of these physicochemical properties. The contents of basic and neutral/acidic drugs in nonpigmented hair are relatively low and the recovery differences among drugs in white hair, regardless of their acidity, basicity, or neutrality of the drug contents are relatively small.
