Effects of vessel geometric irregularity on dissolution test results

Dissolution testing of pharmaceutical products is an important technique used extensively for both product development and quality control, but there are many variables that can affect dissolution results. In this study, the effect of the inner shape of standard 1-L dissolution vessels on drug dissolution results was investigated. The geometric dimensions and irregularities of commercially available vessels (obtained from four different manufacturers) were examined using a three-dimensional video-based measuring machine (VMM). The same analyst, dissolution test assembly, and experimental conditions were used for dissolution testing involving 10 mg of prednisone tablets (NCDA #2) with dissolution apparatus 2 (paddle). Mechanical calibration of the dissolution apparatus was performed prior to dissolution testing with each set of vessels. Geometric characteristics varied within and among the sets of vessels, but the overall averages and standard deviations of dissolution results (six vessels) showed no statistical significant differences among the vessel sets. However, some dissolution differences were noted when comparing individual vessels. With these types of comparisons, the vessel concentricity, sphericity, and radius of sphere were found to possibly influence the amount of prednisone dissolved, but flatness of vessel flange, cylindricity, and circularity showed no effect on dissolution results. The study shows that VMM is a technique that could be used to qualify dissolution vessels.