Apex vessels, previously referred to as PEAK vessels, are commonly used in dissolution experiments with Apparatus 2. They are mentioned in The Dissolution Procedure: Development and Validation 〈1092〉 for their utility in the possible elimination of coning associated with using standard vessels. A Stimuli article, The Case for Apex Vessels, discussing the benefits of including apex vessels in USP–NF general chapters was published in PF 47(6) [Nov.–Dec. 2021]. The objective of the study discussed in the new Stimuli article below was to characterize apex vessels, available from different manufacturers, more comprehensively with the objective of understanding their geometries and associated variabilities. A coordinate measuring machine (CMM) was used to evaluate 37 selected characterization parameters associated with the apex vessel geometries and inherent geometric irregularities. Six vessels, each from seven manufacturers, were characterized. Measurement data was analyzed using skewness plots and statistical tools to understand the variability in all parameters considered. Upon analysis, the apex characterization parameters were found to exhibit intra- and inter-manufacturer variability, indicating variability in the geometries of apex vessels available commercially. Measurements of the geometric irregularities associated with the apexes also presented similar variability across all vessels considered. Results from this study indicate that end-users of apex vessels should be aware of the variabilities in commercially available vessels and should consider controlling the source of apex vessels used with dissolution testing.
