Dose–hair concentration relationship and pigmentation effects in patients on low-dose clozapine

The study investigated the relationship between clozapine dosage and its concentration in hair, focusing on the effects of hair pigmentation. It involved 12 grey-haired patients with Parkinson's disease who were treated with low-dose clozapine. Hair samples were divided into pigmented and non-pigmented portions for analysis. Results showed that clozapine and its metabolite, desmethylclozapine, had a higher affinity for pigmented hair, although they were also present in non-pigmented hair. This suggested that while melanin plays a significant role in drug binding, other hair components also contribute. The study found high correlations between the dose and hair concentration for both clozapine (r = 0.91) and desmethylclozapine (r = 0.88), indicating that hair concentration could reflect the dosage taken.