Amino acids as co-amorphous excipients for tackling the poor aqueous solubility of valsartan

Abstract

Co-amorphization has recently been shown to be a promising approach for stabilizing amorphous drugs and improving the dissolution rate of poorly water-soluble drugs. In this study, three basic amino acids were chosen as small molecular weight excipients to interact with the drug to form co-amorphous combinations. The co-amorphous combinations of valsartan (VAL) with l-histidine, l-arginine, and l-lysine were prepared by vibrational ball milling. Solid-state characterization with X-ray powder diffraction and differential scanning calorimetry (DSC) revealed that all of the co-amorphous mixtures were homogeneous. The molecular interactions of the co-amorphous mixtures were investigated through the glass transition temperature (T_g) in the DSC measurements and Fourier transform infrared spectroscopy. The drug remained chemically stable during the milling process, and the co-amorphous formulations were generally physically stable over at least 3 months at 40 °C under dry conditions. The dissolution rate of all of the co-amorphous mixtures was significantly increased over that of the amorphous VAL alone. The results of this study demonstrated the potential of amino acids as small molecular weight excipients in co-amorphous formulations to improve the drug solubility and dissolution rate.