Hair as a biological specimen for therapeutic drug monitoring.

To study the potential of hair as a biological specimen in therapeutic drug monitoring (TDM), a review of the correlation between hair concentration, blood levels, dose and therapeutic effects of various drugs is presented. The results indicate there is a fair correlation between plasma and hair for several medicines. Moreover, hair samples have the advantage of providing information of more prolonged drug intake, thus allowing a better evaluation of patient compliance. Using segmental hair analysis, only a single sample is necessary. We conclude that hair has potential as a biological specimen in TDM--at least as far as compliance is concerned and possibly as a longer term record of drug concentrations--and that correlation between hair concentration, blood levels and clinical efficacy should be investigated for all drugs where TDM is indicated.