The absorption and fluorescence spectral properties of piroxicam (PRX) in the hydrogenbonding solvents show the most sensitive dependence on the concentration ranging from 8 x 10$^{_5}$ to 2 x10$^{_5}$ M. These are attributed to both the solvent-mediated ground-state intermolecular proton transfer (GSIerPT) leading to formation of the ground state anion and the excited-state intmmolecular proton transfer (ESIraPT). The concentration dependences of the time-resolved emission kinetics at both room temperature and 77 K have also been investigated. It is shown that in the excited state, the ESIraPT of PRX is the dominant process to form a keto tautomer at the high concentration, whereas at the low concentration the excited-state conformational change of the anion is an additional process leading to formation of a zwitterion. The ESI~PT of PRX in the hydrogenbonding solvent is coupled with the ultrafast excited-state solvent reorganization.