definiens: means a derivative of a urid ine nucleoside or nucleotide or a derivative of a cytidine nucleoside or nucleotide in which an acyl substituent derived from a carboxylic acid is attac he d to one or more of the free hydroxyl groups of the r ibose moiety of the nucleoside with an ester linkag e and/or where such a substituent is attached to the amine substituent of the pyrimidine ring of cytidin e, with an amide linkage . Such acyl substituents are d erived from carboxylic acids which include, but are not limited to, compounds selected from the group c onsisting of a fatty acid, an amino acid, nicotinic acid, dicarboxylic acids, lactic acid, p - aminobenzo ic acid and orotic acid . A compound is included in based on its chemical struct ure, regardless of the manner in which it is made