Crystal forms of ketorolac

Four crystal forms of ketorolac have been obtained by recrystallization in organic solvents under variable conditions. Different ketorolac polymorphs and pseudopolymorph were characterized by X-ray powder diffraction crystallography (XRD), Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In the dissolution studies in water at 37 +/- 0.5 degrees C, four crystal forms showed different patterns. The solubility of Form I were the highest. The solubility decreased in rank order: Form I > Form II > Form III > Form IV. Form land Form III were shown to have a good physical stability at room temperature for 60 days. However, Form II is converted to Form III and Form IV is converted to Form I after 60 days storage. Therefore, these observations indicate that crystalline polymorphism for ketorolac is readily inter-convertible and the relationship may have to taken into consideration in the formulation of the drug.