Solid state characterization of an neuromuscular blocking agent--GW280430A.

GW280430A is an ultrashort-acting neuromuscular blocking agent and is targeted for muscle relaxation as part of the intubation surgical procedure. The objective of this work was to perform solid state characterization on GW280430A and to evaluate the relationship between water content and glass transition temperature (Tg). GW280430A was characterized by differential scanning calorimetry, thermogravimetric analysis, powder X-ray diffraction (PXRD), microscopy and moisture sorption. The effect of water content on the Tg of GW280430A was evaluated by equilibrating the material over saturated salt solutions at a range of relative humidities (6.4-72.6%) and determining the Tg by DSC using hermetically sealed aluminum pans. GW280430A undergoes dehydration at 40 degrees C, glass transition at 130 degrees C and decomposition at 190 degrees C by differential scanning calorimetry. By PXRD and moisture sorption, GW280430A is an amorphous material and deliquesces at about 70% RH at room temperature. Water acts as a potent plasticizer for GW280430A and the Tg decreases significantly as the water content increases. No measurable decomposition of GW280430A was observed after 4 weeks at 40 degrees C/75% RH.