The effect of the surface free energy of pharmaceutical tablets on liquid penetration.

The surface free energies (gamma SV) of the integral and partial tablet formulations of an antiarrhythmic drug--cibenzoline succinate, have been assessed by contact angle measurements using high-viscosity polyols and Neumann's equation of state. Independent measurements of penetration for these liquids into the tablets yielded pore size values through the use of the Washburn equation. The role of different constituents of the formulations are analysed in terms of their influence upon the free surface energy of the tablets and penetration rates. The relation between (gamma SV) and penetration rates yields for a series of liquids two threshold values: (gamma SV)s 'start' and (gamma SV)r, 'rapid', which define respectively the beginning of the measurable penetration and the rapid penetration.