Solubility Enhancement of Ritonavir: Co-Crystallization

The main objective of this work is to explore co-crystallization approach for increasing solubility of an antiretroviral drug, Ritonavir (RTN). In this study, different co-formers with different functional groups like carboxylic acid andacid amidewere tried in ratio of 1:1, 1:2 and 1:3 (RTN:Co-former) using neat grinding method. Co-formers used were citric acid (CIT) and adipic acid (ADP). The co-crystals formed were characterized by melting point determination, Fourier-transform infrared (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and solubility studies. Co-crystals of drug with CIT and ADP showed the improved dissolution profile when compared to the pure RTN. Melting point, DSC, FTIR spectra of co-crystals were different than pure drug and co-formers indicating their interaction. XRD patterns of co-crystals were not completely amorphous but less intense compared to drug alone.