Thermal characterization of lovastatin in pharmaceutical formulations

Abstract

Thermogravimetry (TG) and differential scanning calorimetry (DSC) are useful techniques that have been successfully applied in the pharmaceutical industry to reveal important information regarding the physicochemical properties of drug and excipient molecules such as polymorphism, stability, purity, and formulation compatibility among others. In this study, lovastatin was studied by TG, DSC, and other techniques such as Fourier transform infrared spectroscopy, optical microscopy, X-ray diffraction, chromatography, and mass spectrometry. Lovastatin showed melting point at 445 K and thermal stability up to 535 K. It presented morphological polymorphism, which in the drug has the same unit cell, but with different crystal habits. Preservative excipient butylhydroxyanisole (BHA) causes amorphization of lovastatin crystallites and, therefore is incompatible with lovastatin. Degradation by hydrolysis was observed under neutral, acid, and basic conditions. The active degradation product, lovastatin hydroxyacid, was obtained after neutral and basic hydrolysis.