Physical model approach to taste studies of drugs and pharmaceutical formulations.

This paper explores the physical model approach in studying the taste of drugs and assessing physical formulation factors for improving the undesirable taste of drugs. Various aspects of physiology relevant to the taste phenomenon have been reviewed to provide the biophysical basis for mathematical modeling. The model involves non-steady-state mass transport across the aqueous boundary layer and buildup of solute concentration at the essentially impermeable tongue surface. The theoretical predictions are consistent with experimental studies on the lag time to taste perception by the electrophysiological method and also with "instantaneous" psychophysical taste perception when solute concentrations much greater than the taste threshold are applied on the tongue. Within the framework of the non-steady-state model, novel experimental studies involving the use of a porous half-diffusion cell placed on the surface of an extended human tongue and the recording of the times for psychophysical taste response are proposed to quantify and provide mechanistic understanding of the taste of drugs and also physical formulation factors in overcoming undesirable taste properties.