Flunixin meglumine: a non-narcotic analgesic

The N-methyl-d-glucamine salt of flunixin (flunixin meglumine) is a potent non-narcotic analgesic agent after parenteral administration in mice, rats and monkeys. It is significantly more potent than pentazocine, meperidine and codeine in the rat yeast paw test after subcutaneous administration in saline. Activity on intramuscular administration is comparable to that after subcutaneous administration and is enhanced when dissolved in buffered saline as compared to nonbuffered saline. In addition, flunixin meglumine also had oral activity and differs from indomethacin in having more analgesic activity per unit of anti-inflammatory activity. In mice, flunixin meglumine is equipotent to pentazocine and more potent than meperidine and codeine in the abdominal constriction test. In primates, flunixin meglumine at 10 mg/kg i.m., produced a degree of analgesic efficacy comparable to that of a clinically effective dose of morphine (0.3 mg/kg). In contrast to codeine, tolerance to the analgesic action of flunixin meglumine was not observed. Furthermore, flunixin meglumine retained its activity in rats made tolerant to codeine. Unlike narcotics, the analgesic effect of flunixin meglumine is not antagonized by naloxone after acute administration in rats. These results indicate that flunixin meglumine is a parenterally and orally effective analgesic in animals and is unlikely to have narcotic or drug dependence liability.