Tablet-crushing strength along with tablet weight, thickness, and diameter were determined using an automatic tablet-testing system (AT4, Dr. Schleuniger Pharmatron, Switzerland). The tablet-crushing strength data reported are the mean of 10 individual determinations. Tablet weight and thickness were tested; the data are not reported here but they were controlled in a tight range.

Tablet friability was measured on a friabilator (VanKel Friabilator, VanKel Industries, Edison, NJ) rotated at 25 rpm for 5 min. Twenty tablets per sample were randomly selected for the study. The friability for each sample was calculated using the following equation:

Friability (%) = (Wb–Wa) / Wb ×100

All initial tablet characterization studies (tablet-crushing strength, disintegration time, and friability) were performed on tablets that were stored for 24 h at ambient conditions in tightly closed and doubled plastic bags. The tablets were stored at ambient conditions in the same tightly closed and doubled plastic bags for four months, and tablet-crushing strength, disintegration time, and friability were reevaluated using the same procedures as the initial studies.

Triangle mouthfeel study of ODTs. Sensory science is a scientific method used to measure, analyze, and interpret human responses to products as perceived through their senses of touch, taste, sight, smell, or sound (10). There are many different types of sensory tests. For example, attribute difference tests measure certain qualities or trait differences between samples. Affective sensory tests measure consumer acceptance of a product. Overall difference tests measure sensory differences between samples. A triangle test is a type of overall difference test to determine if there is a sensory difference between two products. Here, the triangle mouthfeel test was performed to determine if there were any mouthfeel differences between ODTs that contain 2% Ac-Di-Sol (crosslinked croscarmellose sodium, XL-CMC, FMC, Philadelphia, PA) and ODTs that contain 5% PVP XL-10 (Crospovidone, ISP, Wayne, NJ), when all the other ingredients remain the same. Ac-Di-Sol and PVP XL-10 were chosen for study because they are the two most popular superdisintegrants and very effective at their optimal use level. These tablets were all compressed at 8kN.

ODTs that contained 2% Ac-Di-Sol were coded with two different three-digit numbers (e.g., 767, 189). ODTs that contained 2% PVP XL-10 were coded with two different sets of three-digit numbers (e.g., 312, 570). In each set of the study, three coded ODT samples were presented to a panelist. For example, the three samples could be numbered 767-312-189, which represented two identical ODTs that contain 2% Ac-Di-Sol plus one ODT that contains 5% PVP XL-10; or numbered 570-312-189, which represented two identical ODTs that contain 5% PVP XL-10 plus one ODT that contains 2% Ac-Di-Sol. Each panelist was informed that he or she received three coded samples—two were identical, and one was different. To further reduce influencing the panelists' decisions, coded samples were presented in a random order to different panelists. Each panelist was asked to test the ODT samples from left to right, and each rinsed his or her mouth with water between each test. Each panelist identified one sample he or she felt was different from the other two in terms of mouthfeel and was asked to describe the difference in the comments section. The difference in mouthfeel may have been described as disintegration time, taste, or texture. A total of 34 ODT sample sets (102 tablets) were tested by 34 panelists. Responses were collected and used to draw a statistical conclusion.

Texture analyzer evaluation of ODTs. A texture analyzer (TA-XT2i, Texture Technologies, Scarsdale, NY) was used to monitor the disintegration process of ODTs in shallow water. The settings were "measure distance in compression, hold until time" with a 5-kg load cell, ½-in. diameter clear, cylindrical probe. The automatic surface detection trigger was set to 1 g, with a pretest speed of 1 mm/s and a test speed of 0.1 mm/s. For each test, a small weighing boat with 2 mL of deionized water was placed under the probe with a height set at 7 mm. The ODT to be tested was put into the 2mL water, and the test started simultaneously.