The present invention relates to improved therapeutically active nanocomposite microstructure compositions, including nanoparticle compositions and nanoparticle preparations. Preferred embodiments include nanoparticle compositions comprising nanoparticles of a therapeutically active agent dispersed in a carrier matrix. The invention also relates to a method for preparing said compositions and preparations using solid-state mechanochemical synthesis. Further, it relates to therapeutic products produced using said compositions and to methods of treatment using the compositions.