Uncharacterized and uncharacterizable attributes of macromolecular excipients
Shireesh Apte · International Journal of Pharmaceutical Excipients · 2016
Macromolecular excipients are unique in that each (macro)molecule or polymer chain can chemically differ significantly from another. However, these differences may not be detected across different lots or different samples because the analytical methods used to characterize such samples typically can only detect the average of the different individual molecular chemical attributes. As a result, it may be possible that different lots of macromolecular excipients that nominally conform to certain set specifications (degree of substitution, molar substitution, % content of hydroxypropyl groups) may yet contain subpopulations, whose chemical attributes may differ widely from the average, and also differ widely from subpopulations in other lots. Analytical method limitations (for macromolecules), thus force the categorization of such attributes as being ‘un-characterizable’.