Abstract: Novel ester derivatives of carboxylic acid medicaments of formula (I), wherein R--COO--represents the acyloxy residue of a carboxylic acid drug or medicament, n is an integrer from 1 to 3, and R.sub.1 and R.sub.2 are the same or different and are selected from a group consisting of an alkyl, an alkenyl, an aryl, an aralkyl, a cycloalkyl and which group may be unsubstituted or substituted, or R.sub.1 and R.sub.2 together with the N forms a 4-, 5-, 6- or 7-membered heterocyclic ring, which in addition to the nitrogen atom may contain one or two further heteroatoms selected from the group consisting of nitrogen, oxygen and sulfur and which heterocyclic group may be substituted. These compounds are highly biolabile prodrug forms of the corresponding carboxylic acid compounds and are highly susceptible to undergoing enzymatic hydrolysis in vivo whereas they are highly stable in aqueous solution.