A novel off-center paddle impeller (OPI) dissolution testing system for reproducible dissolution testing of solid dosage forms.

Dissolution testing is routinely conducted in the pharmaceutical industry to provide in vitro drug release information for quality control purposes. The most common dissolution testing system for solid dosage forms is the United States Pharmacopeia (USP) Dissolution Testing Apparatus 2. This apparatus is very sensitive to the initial location of the tablet, which cannot be controlled because the tablet is dropped into the vessel at the beginning of the test and it may rest at random locations at the vessel's bottom. In this work, a modified Apparatus 2 in which the impeller was placed 8 mm off center in the vessel was designed and tested. This new design was termed "OPI" for "off-center paddle impeller." Dissolution tests were conducted with the OPI apparatus for nine different tablet locations using both disintegrating tablets (prednisone) and nondisintegrating tablets (salicylic acid). The dissolution profiles in the OPI apparatus were largely independent of the tablet location at the vessel's bottom, whereas those obtained in the Standard System generated statistically different profiles depending on the tablet location. The newly proposed OPI system can effectively eliminate artifacts generated by random settling of the tablet at the vessel's bottom, thus making the test more robust.