Simultaneously improving tabletability and solubility of diclofenac by cocrystallization with picolinamide

Diclofenac (DIC) is a nonsteroidal anti-inflammatory drug with poor tabletability and water solubility. In the present study, a new diclofenac-picolinamide cocrystal (DIC-PIC) was prepared to simultaneously improve its tabletability and solubility. The cocrystal was characterized using multiple techniques, such as X-ray diffraction, thermal methods and spectral analyses. The tabletability of DIC-PIC was significantly improved over DIC, which is attributed to the larger bonding area between crystals due to the higher plasticity of DIC-PIC, demonstrated by the lower in-die mean yield pressure, P_y,i, of DIC-PIC (59.5 ± 0.6 MPa) than DIC (86.6 ± 1.4 MPa). The higher plasticity of DIC-PIC is consistent with the existence of a slip plane (001) in its crystal structure. The thermodynamic solubility of DIC-PIC is significantly higher than that of DIC (112 times higher in water and 22 times higher in pH = 6.8 buffer solution). Hence, the simultaneous improvement in tabletability and solubility of DIC-PIC overcomes two main barriers in developing DIC tablets, which makes it a promising candidate for developing a DIC tablet with improved performance.