Methods for the manufacture of medicinal compositions are described. A method for the manufacture of a medicinal composition according to the invention comprises: (a) Providing a biocompatible polymer of the general formula —[O—R1—C(O)]n— wherein: “R1” is a linear, branched, or cyclic organic group, “n” is at least three, (b) Acylating the biocompatible polymer to provide an acylated biocompatible polymer and a mixed anhydride; (c) Reacting the mixed anhydride with a nucleophile to provide an acylated biocompatible polymer with a terminal carboxylic acid derivative capable of being chemically converted to an acid in the absence of water, (d) Converting the terminal carboxylic acid derivative to an acylated biocompatible polymer with a terminal carboxylic acid; and (e) Combining the acylated biocompatible polymer with a drug to provide the medicinal composition.