In vitro activity: (R, S)-, (S)-, and (R)-Ketorolac inhibit both isoforms of COX in recombinant rat and human enzyme systems, and similar as inhibitors of rat COX (rCOX) and human COX (hCOX) under the conditions used. (R, S)-Ketorolac inhibits rat COX-1, rat COX-2, human COX-1 and human COX-2 with IC50 of 0.27 μM, 2.06 μM, 1.23 μM and 3.50 μM, respectively. The (S) enantiomer of Ketorolac with IC50 of 0.10 μM for rat COX-1 is approximately twice as potent as the racemate, whereas the (R)-enantiomer with IC50 of > 100 μM is virtually without activity. Ketorolac shows inhibition of eicosanoid formation in HEL cells (COX-1) and LPS-stimulated Mono Mac 6 cells (COX-2) with IC50 of 0.025 μM and 0.039 μM, respectively, 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

Kinase Assay: Recombinant COX-1 and COX-2 from rat (rCOX) and human (hCOX) expressed in a baculovirus system are purified and reconstituted with 2 mM phenol and 1 μM hematin. Then the cyclooxygenase activity is measured using a radiometric assay, and the specific activity of the final enzyme preparations used is between 20,000 and 35,000 units. Ketorolac (2 -15 μL) are diluted in DMSO and preincubated with the appropriate recombinant COX (3 -15 ng) at a final concentration of 0.01 to 1000 μM in a reaction mixture (150 μL) containing 50 mM Tris-HCl buffer (pH 7.9), 2 mM EDTA, 10% glycerol, 2 mM phenol, and 1 μM hematin for 10 minutes. The reaction is initiated by addition of [14C]arachidonic acid (50–60 mCi/mmol in a final concentration of 20 μM) and is terminated 45 seconds later by the addition of 100 μL of 0.2 N HCl and 750 μL of distilled water. The total reaction volume is then applied to a 1 mL C18 Sep-pak column that has previously been washed with 2 mL of methanol followed by 5 mL of deionized water. Oxygenated products are eluted with 3 mL of a mixture of acetonitrile/water/acetic acid (50:50:0.1, v/v/v) and quantified by liquid scintillation spectroscopy. 

Cell Assay: Human osteoblasts cells are exposed to Ketorolac for 24 hours. Thymidine incorporation is assessed by the TopCount Microplate Scintillation and Luminescence Counters through adding [3H]-thymidine to cultures 4 hours prior to harvesting. Cell cycle distribution is determined by using propidium iodide in flow cytometer, and cell apoptosis or necrosis is detected using the Annexin V-FITC Apoptosis Detection Kit.