Examination of a long-term clozapine administration by high resolution segmental hair analysis

Significant and reproducible concentration profiles along the hair fibres revealed characteristic administration cycles. The administration time course -in particular the time of its termination-could be verified with a precision of a few days. The accuracy and reproducibility of the concentration profile was proven based on multiple investigations of single hairs. An individual hair growth rate of 0.55 mm/day was determined with a relative standard deviation of 8% by comparison of concentration profiles in hairs collected after a time span of 165 days.