The purpose of the present study was to establish a novel method to evaluate water penetration rates by combining the local dynamic contact angle and thermographic approach to characterize water conduction properties in orally disintegrating (OD) tablets. The OD tablet tester OD-mate was used to measure the disintegration times of OD tablets. Other formulation characteristics, such as tablet hardness and friability, were evaluated. By examining three formulation characteristics, such as the disintegration time, tablet hardness, and friability, of 33 OD tablets for generic drugs, four characteristic OD tablets containing aripiprazole were selected. To quantitatively evaluate water penetration rates into the tablet interior, we measured the dynamic contact angle after dropping water locally on the tablet surface. Linearity with a high correlation coefficient was observed for each of the initial time-dependent changes in the dynamic contact angle. Water penetration rates into tablets were approximately twice as fast for Pharmaceuticals A and B than for Pharmaceuticals C and D. These rates were consistent with changes observed in tablet thermographic imaging. The relationship between the rapid disintegration of the tablet and its physical strength was discussed based on the internal structure of the tablet by X-ray CT and the additives of each OD tablet. The present results demonstrated that the water penetration rates of OD tablets, as measured by dynamic contact angle, may accurately detect differences in disintegration times in the human oral cavity.
Keywords: OD-mate; disintegration time; dynamic contact angle; infrared thermography; orally disintegrating tablet; water penetration rate.