Comparison of ketorolac tromethamine with other injectable nonsteroidal anti-inflammatory drugs for pain-on-injection and muscle damage in the rat.

The local tolerance of ketorolac tromethamine (Toradol, Syntex) was compared with that of four other injectable nonsteroidal anti-inflammatory drugs (NSAIDs) (diclofenac sodium, piroxicam, ketoprofen, and metamizol magnesium) in the rat paw-lick/muscle irritation assay as described previously. All drugs were tested at concentrations approved for clinical use. After subplantar (footpad) injection, ketorolac produced virtually no pain-on-injection as assessed by the number of paw-lick/lift responses during a 15 min observation period. The other NSAIDs produced slight to moderate paw-lick/lift responses. Redness and swelling at the injection site were less severe for ketorolac than for the other NSAIDs. After intramuscular (i.m.) injection, all of the NSAIDs produced some degree of muscle damage, as assessed histopathologically 24 h after injection. The lesions, consisting primarily of muscle degeneration, were less severe for ketorolac than for the other NSAIDs. Ketorolac and metamizol produced the smallest elevations in serum creatine kinase, as measured 2 h after i.m. dosing, not significantly different from isotonic saline. Overall, ketorolac was better tolerated in the assay than the other injectable NSAIDs, thereby suggesting the possibility of improved local tolerance on clinical use.