These studies were performed to determine the effects of cyclooxygenase (COX)inhibition with nonsteroidal anti-inflammatory agents (NSAIDs) that were either COXnonselective(ibuprofen) or a preferential inhibitor of COX-2 (carprofen or etodolac) or a COX-2selective agent (deracoxib) on renal function in euvolemic dogs and in dogs with extracellularfluid volume depletion. Plasma and urine biochemistries and urinary clearances of creatinine andpara-aminohippuric acid were used to assess glomerular filtration rate (GFR) and renal plasmaflow (RPF), respectively, in dogs with and without chronic administration of a 4 mgfurosemide/kg body weight orally twice daily for 8 days. The effects of oral administration ofibuprofen (10 mg/kg once daily) and carprofen (2.2 mg/kg twice daily) and etodolac (12.5 mg/kgonce daily) and deracoxib (3.5 mg/kg once daily) were compared utilizing a randomizedcrossover design. The results showed in dogs receiving furosemide, ibuprofen and carprofen hadsignificant decreases in GFR but not RPF. The results of the first study revealed decreases inGFR when either NSAID was administered to dogs with volume-depletion induced byfurosemide administration. The renal effects of the COX-nonselective and the preferential COX2inhibitor were not significantly different. The results of the second study revealed that neithercarprofen nor etodolac had a significant effect on RPF or GFR when administered alone. In dogsreceiving furosemide, both carprofen and etodolac resulted in a significant, reversible decrease inGFR compared to placebo treatment. These results show when carprofen and etodolac wereadministered to dogs with volume-depletion it may be deleterious to renal function. The thirdstudy revealed a decrease in GFR when carprofen and etodolac and deracoxib were administeredto dogs in combination with furosemide. The renal effects of the COX-nonselective, preferentialCOX-2 inhibitors and a coxib were similar. Using an NSAID of any type in dogs withextracellular fluid volume depletion may be deleterious to renal function.