The present invention is based on the discovery that a marked increase in aqueous stability (and thereby shelf life) of prostanoid agonist prodrug compositions is achieved by incorporating into the compositions certain well-defined carboxylic acids, and thereafter adjusting the pH of the compositions from about 4.0 to about 8.0. As a result, the compositions and methods of the invention provide the aqueous stability required for marketable topical drug treatments of a wide variety of ocular disorders.
