Abstract
Selection of an optimal salt form of a drug candidate is a vital component of preformulation stage of drug development. In this study, six salts of enalapril – citrate, mesylate, tartrate, malate, besylate and tosylate – were prepared and characterized by Mass Spectroscopy, Differential Scanning Calorimetry, Thermogravimetric Analysis, Microscopy, Powder X-ray Diffraction, Karl Fischer Titration, High Performance Liquid Chromatography, Fourier-Transform Infra-red Spectroscopy and Head Space Gas Chromatography. All the six salts were subjected to a tiered screening involving five stages in the following order: crystallinity, hygroscopicity, solubility, stability and flow/compactability. Enalapril malate showed encouraging profile because of its lower hygroscopicity, higher solubility, good solid state stability, and better flow and compactability, in comparison to the marketed maleate salt.
ACKNOWLEDGMENTS
The author expresses gratitude to Sri Krishna Pharmaceuticals, India, for providing the sample of enalapril maleate USP. Services provided by Central Instrumentation Lab, NIPER, are also gratefully acknowledged.