Detection of Tiludronic Acid in Equine Hair and Its Segmental Analysis Following Administration

A method for the detection of tiludronic acid in equine hair was developed and applied to investigate its distribution in hair following administration of Tildren®. Hair samples collected from seven horses at 2-7 months post-administration were analysed using ultra-performance liquid chromatography tandem high-resolution mass spectrometry (UPLC–MS/HRMS). The method achieved an estimated limit of detection of 0.1 pg/mg. Tiludronic acid was detected in all hair samples collected following administration. Segmental analysis revealed non-uniform distribution along the hair shaft, with the highest concentrations observed in discrete segments corresponding to the time of drug exposure. The position of the concentration peak shifted towards distal end with increasing post-administration time according to the normal hair growth rate. These findings demonstrate the incorporation of tiludronic acid into equine hair via systemic circulation and suggest that segmental hair analysis may provide information regarding the timing of bisphosphonate exposure in horses.