An etoricoxib phase diagram: Hemihydrate and anhydrate

Anhydrate and hemihydrate phases of etoricoxib (5-chloro-6‘-methyl-3-[4-(methylsulfonyl)phenyl]-2,3‘-bipyridine) are described. The ternary phase diagram of etoricoxib, isopropyl acetate, and water at 10 °C is reported. The critical water/isopropyl acetate ratio at this temperature, below which etoricoxib will exist as anhydrate at equilibrium, is 0.21 ± 0.04 wt % water, as determined from measurements made on the ternary solution in simultaneous equilibrium with anhydrate and hemihydrate solids.