The plasticising effect of supercritical CO 2 during the solvent-free melt extrusion of the cationic copolymer Eudragit E and the heat-sensitive and slowly dissolving active pharmaceutical ingredient, spironolactone was shown to reasonably improve the purity of the prepared solid dispersions by enabling production at lower temperature ranges. By increasing the mass flow of the melt, further enhancement was achieved in purity, but the shorter residence time counteracted the amorphisation (i.e. molecular dispersion) of crystalline drug particles, according to data acquired by confocal Raman mapping. At the same time, supercritical CO 2 aided amorphisation of the lipophilic drug, thus also facilitating the production of fully amorphous glassy solution samples at the lowered temperature. The obtained high amorphicity ensured immediate drug dissolution in acidic medium. Scanning electron microscopy revealed that optimal extrusion parameters enabled the production of foams of low porosity, homogeneous structure and thin walls.