SURFACE BINDING-STUDIES OF SPIN-LABELED PIROXICAM BY ELECTRON-PARAMAGNETIC-RESONANCE

Piroxicam is a highly potent anti-inflammatory and analgetically activ e drug the bioavailability of which is affected by its low solubility and dissolution rate. To modify its dissolution characteristics, solve nt deposits of piroxicam and spin-labelled piroxicam iperidin-4-yl)-2H -1,2-benzothiazine-3-carboxamide, 1,1-dioxide) on silica (amorphous no n-porous silicon dioxide) or on sodium chloride crystals were prepared . Electron paramagnetic resonance (EPR) spectra reveal the distributio n and packing of molecules on the surface of the carriers. For concent ration ranges up to 3.10(-5) mol g-1 silica (greater-than-or-equal-to 0.06 molecules nm-2) the relative populations of agglomerates and spar ingly populated regions were detected, including the possible rearrang ement of deposited piroxicam molecules upon heat treatment. The relati ve dissolution rates conform with the population of the agglomerated f raction of piroxicam.