Phase Equilibrium in the Caffeine–Paracetamol–Piracetam Triple Condensed System. Study of some Pharmaco-Technological Parameters of the Eutectic Composition

A set of thermoanalytical methods and the well-known methodological principle of composition–property relationship were used to find the optimum composition of the caffeine–paracetamol–piracetam model disperse system with preset in vitro pharmaceutical characteristics. The work was aimed at studying phase diagrams of the related condensed system and several technological parameters of the tableted composition form corresponding to an invariant point on the phase (melting) diagram of this system. The thermal properties of the binary component subsystems and then the ternary system itself were studied in air on a DSC-500 differential scanning calorimeter (Russia) in the range 20 – 250°C in heating mode at 10°C/min. Rectangular phase (melting) diagrams of the systems paracetamol–piracetam, caffeine–paracetamol, and caffeine–piracetam were constructed based on the onset temperatures of deviation of the DSC curves from the thermogram baselines of individual compositions. Data on phase equilibria in the caffeine–paracetamol–piracetam ternary system were presented. A eutectic of the ternary system was observed at a component ratio of 8:48:44 mass% (or 3.7:29:67.3 mol%), respectively, with a melting point of 90.6°C. The binary eutectic mixtures related to the ternary system being considered and the ternary eutectic dispersion were shown to differ from mixtures with other ratios of the same series by improved compressibility and release of active components. Tablets obtained from the eutectic dispersions by direct pressing were characterized by increased mechanical abrasion resistance and compression strength under standard test conditions.