Influence of solvents on the crystal habit and properties of rofecoxib and celecoxib: No evidence of polymorphism

Abstract

Background: In many cases, drugs can exist in more than one crystalline form; the
phenomenon is known as “polymorphism.” Though the polymorphs are chemically
identical, they exhibit different physicochemical properties, viz., melting point,
solubility, X-ray diffraction pattern, etc., which further affect the biological properties
of drugs. The purpose of this work was to study the effect of solvents on crystallization,
solubility and dissolution of rofecoxib and celecoxib. Materials and Methods: The
crystals were prepared by using different solvents. The melting point, solubility,
dissolution, Fourier-transformed infrared (FT-IR), X-ray diffraction (XRD), differential
scanning calorimetry (DSC) and scanning electron microscopy (SEM) studies were
carried out to confirm the polymorphism in drugs. Result: The results indicate that
the crystals obtained from different solvents exhibited different physicochemical
properties. Though FT-IR and XRD gave an indication of different crystal morphs,
DSC proved absence of any polymorphic behavior in the crystals of rofecoxib and
celecoxib. Conclusion: Crystals having the desired physicochemical properties may
be obtained by selecting solvents of specific polarities.