The potential of a sustained release formulation for paracetamol produced by melt pelletisation was investigated. The
chosen formulation was based on the combination of stearic acid as a melting binder and anhydrous lactose as a filler. After
determination of the size distribution, the pellet characterisation included scanning electron microscopy (SEM), X-ray
photoelectron spectroscopy (XPS), specific surface area and true density determination. Hence, the in vitro release from
every single size fraction (2000, 1250, 800, 630, ,630 mm) was evaluated and the release mechanism was analysed with the
help of an appropriate mathematical model. The results of drug content and superficial atomic composition were found to be
constant in all pellets size fractions, attesting the ability of melt pelletisation in a high shear mixer to form a product with
homogeneous composition. The mathematical model is built on the hypotheses that drug diffusion and solid drug dissolution
in the release environment are the key phenomena affecting drug release kinetics. Smaller classes apart (particles are not
perfectly spherical), the comparison between model best fitting and experimental data indicated the reasonability of these
hypotheses. Moreover, model reliability is proved by its ability of predicting drug release from a known mixture of the above
mentioned particles classes.
