The simple answer is no. For example, polyethylene glycol is more commonly being used in the
manufacture of bulk or recombinant proteins in essence becoming a part of the API. Should this
be considered a more critical starting material? Yes, when it is covalently linked with the protein
or other macromolecule. It is certainly no longer an excipient. In fact it is now part of the API and
is certainly critical with a fairly high priority.
