The present invention relates to a method and an improved composition for improving the absorption of an ester prodrug in a subject. The method includes co-administering to the subject an effective amount of the ester prodrug or a pharmaceutical acceptable salt thereof, and a sufficient amount of adjuvant to impede a carboxylesterase-mediated hydrolysis of the ester prodrug in vivo, wherein the adjuvant is selected from the gnzup consisting of triacetin, triethyl citrate and a combination of both. The present invention also relates to a method for impeding carboxylesterase-mediated hydrolysis of esters, including ester prodrugs.
