A new class of hybrid nitric oxide-releasing anti-inflammatory (AI) ester prodrugs (NONO-coxibs) wherein an O(2)-acetoxymethyl-1-(N-ethyl-N-methylamino)diazen-1-ium-1,2-diolate (13a-b), or O(2)-acetoxymethyl-1-(2-methylpyrrolidin-1-yl)diazen-1-ium-1,2-diolate (16a-b), NO-donor moiety was covalently coupled to the COOH group of 5-(4-carboxymethylphenyl)-1-(4-methane(amino)sulfonylphenyl)-3-trifluoromethyl-1H-pyrazole (11a-b) was synthesized. The percentage of NO released from these diazen-1-ium-1,2-diolates was significantly higher (59.6-74.6% of the theoretical maximal release of 2 molecules of NO/molecule of the parent hybrid ester prodrug) upon incubation in the presence of rat serum, relative to incubation with phosphate buffer (PBS) at pH 7.4 (5.0-7.2% range). These incubation studies suggest that both NO and the AI compound would be released from the parent NONO-coxib upon in vivo cleavage by non-specific serum esterases. All compounds were weak inhibitors of the COX-1 isozyme (IC(50)=8.1-65.2microM range) and modest inhibitors of the COX-2 isozyme (IC(50)=0.9-4.6microM range). The most potent parent aminosulfonyl compound 11b exhibited AI activity that was about sixfold greater than that for aspirin and threefold greater than that for ibuprofen. The ester prodrugs 13b, 16b exhibited similar AI activity to that exhibited by the more potent parent acid 11b when the same oral mumol/kg dose was administered. These studies indicate hybrid ester AI/NO donor prodrugs of this type (NONO-coxibs) constitute a plausible drug design concept targeted toward the development of selective COX-2 inhibitory AI drugs that are devoid of adverse cardiovascular effects.