The aim of this study was to develop a LC-MS/MS method for the quantification of PHT on DBS This analytical method was validated and gave good linearity (r2= 0.999) in the range of 0–100 mg/l. LOQ and LOD were 1.0 mg/l and 0.3 mg/l, respectively The drug extraction from paper was performed in a few minutes using a mixture composed of organic solvent for 80%
The recovery ranged from 85 to 90%; PHT in DBS showed to be stable at different storage temperatures for one month A good correlation was also obtained between PHT plasma and DBS concentrations This method is both precise and accurate and appears to be particularly suitable to monitor treatment with a simple and convenient sample collection procedure.