Ketorolac (tromethamine salt) inhibits both isoforms of Cox in recombinant rat and human enzyme systems. Ketorolac inhibits rat Cox-1 (IC50 of 0.27 μM), rat Cox-2 (IC50 of 2.06 μM), human Cox-1 (IC50 of 1.23 μM) and human Cox-2 (IC50 of 3.50 μM). The (S) enantiomer of Ketorolac with rat Cox-1 (IC50 of 0.10 μM) is approximately twice as potent as the racemate, whereas the (R)-enantiomer (IC50 of > 100 μM) is virtually without activity. Ketorolac shows inhibition of eicosanoid formation in HEL cells (Cox-1, IC50 of 0.025 μM) and LPS-stimulated Mono Mac 6 cells (Cox-2, IC50 of 0.039 μM), but does not significantly inhibit NO accumulation in supernatants of LPS-stimulated RAW 264.7 cells up to 300 μM. Ketorolac significantly inhibits thymidine incorporation of human osteoblasts (hOBs) upon 24 hours treatment in a dose-dependent manner, and inhibits proliferation and arrests cell cycle at G0/G1 phase in hOBs. Ketorolac (tromethamine salt) inhibits both isoforms of Cox in recombinant rat and human enzyme systems. Ketorolac inhibits rat Cox-1 (IC50 of 0.27 μM), rat Cox-2 (IC50 of 2.06 μM), human Cox-1 (IC50 of 1.23 μM) and human Cox-2 (IC50 of 3.50 μM). The (S) enantiomer of Ketorolac with rat Cox-1 (IC50 of 0.10 μM) is approximately twice as potent as the racemate, whereas the (R)-enantiomer (IC50 of > 100 μM) is virtually without activity. Ketorolac shows inhibition of eicosanoid formation in HEL cells (Cox-1, IC50 of 0.025 μM) and LPS-stimulated Mono Mac 6 cells (Cox-2, IC50 of 0.039 μM), but does not significantly inhibit NO accumulation in supernatants of LPS-stimulated RAW 264.7 cells up to 300 μM. Ketorolac significantly inhibits thymidine incorporation of human osteoblasts (hOBs) upon 24 hours treatment in a dose-dependent manner, and inhibits proliferation and arrests cell cycle at G0/G1 phase in hOBs. A non selective inhibitior of Cox-1 and Cox-2.