Predictive thermodynamic modeling and experimental measurements on solubility of active pharmaceutical ingredient: Lornoxicam case study

Abstract Low solubility of some drugs in water is a challenging issue in pharmaceutical area which should be properly addressed to achieve drugs with high efficacy. The solubility of an active pharmaceutical ingredient (API) namely lornoxicam in carbon dioxide at supercritical conditions is measured in this work. The experimental measurements were carried out utilizing gravimetric technique, at the pressure and temperature intervals of 120–400 bar and 308–338 K, respectively. The determined mole fraction of solubility revealed that the solubility of this drug is between 3.08 × 10−5 to 3.54 × 10−4. It was perceived that pressure has strong and direct effect on the solubility in which the solubility increases with rising system's pressure. Unlike pressure, the effect of temperature depends on the cross-over point which is between 160 and 200 bar for lornoxicam. Above the cross-over point, the solubility indicated direct relationship with temperature due to improvement of sublimation pressure which is the dominant mechanism. In addition to the experimental measurements, the solubility data are correlated using five semi-empirical correlations namely Mendez-Santiago-Teja (MST), Bartle et al., Chrastil, Kumar and Johnston (KJ) and Garlapati & Madras with minimum average absolute relative deviation (AARD %) 6.2% for Bartle et al. model.