IC50: A potent cyclooxygenase inhibitor with IC50 values of 1 nM.

Flunixin meglumine serves as a non-narcotic and non-steroidal analgesic agent with antipyretic activities. As a potent inhibitor of the enzyme cyclooxygenase, Flunixin meglumine has demonstrated a wide-spectrum of biological activities including anti-inflammation and pain-alleviating. Moreover, Flunixin meglumine could be applied as a drug in animals for the management of intestinal ischaemia, colic, and endotoxemia. [1]

In vitro: An in vitro whole blood model in feedlot calves was adopted to detect the activity of the anti-inflammatory agents Flunixin-meglumine (FLU), RS (±) Carprofen (CPF) and S (+) CPF. The drugs all exhibited inhibitory activity on COXs, with an order of FLU > S (+) CPF > RS (±) CPF in their potency. This finding indicated that FLU was a nonselective suppressorr of bovine COXs, whereas RS (±) CPF and S (+) CPF selectively inhibited COX-2 isoenzyme. [2]

In vivo: Findings from mice, rats and monkeys suggested Flunixin meglumine as a potent non-narcotic analgesic agent after parenteral administration. After being subcutaneous administered, this agent showed higher efficacy than pentazocine, meperidine and codeine in the rat yeast paw test. Intramuscular administration and subcutaneous administration of Flunixin meglumine had similar effects. Moreover, orally administered Flunixin meglumine also exerted analgesic and anti-inflammatory activities. Based on mice abdominal constriction test, flunixin meglumine had comparable efficacy to pentazocine and was more potent than meperidine and codeine. In primates, 10 mg/kg flunixin meglumine showed an equal efficacy to that of 0.3 mg/kg morphine. [1]

Clinical trials: Flunixin meglumine, in a dosage of 1.0 mg/kg bwt, was studied in a blind Multi-Centre clinical trial in 152 horses with abdominal pain. Significant differences were noted in kicking, pawing, head and body movement and attitude between the horses receiving flunixin meglumine and control. Moreover, compared with detomidin, Flunixin meglumine provided significantly less analgesia. [3]

References:
[1]Ciofalo VB, Latranyi MB, Patel JB and Taber RI.  Flunixin meglumine: a non-narcotic analgesic. J Pharmacol Exp Ther. 1977 Mar; 200(3): 501-7.
[2]Miciletta M, Cuniberti B, Barbero R and Re G.  In vitro enantioselective pharmacodynamics of Carprofen and Flunixin-meglumine in feedlot cattle. J Vet Pharmacol Ther. 2014 Feb; 37(1): 43-52.
[3] Jochle W, Moore JN, Brown J, Baker GJ, Lowe JE, Fubini S, Reeves MJ, Watkins JP and White NA.  Comparison of detomidine, butorphanol, flunixin meglumine and xylazine in clinical cases of equine colic. Equine Vet J Suppl. 1989 Jun; (7): 111-6.