Pharmacodynamic evaluation of the peripheral pain inhibition by carprofen and flunixin in the horse.

The research tested the effectiveness of two drugs, carprofen and flunixin meglumine, in relieving pain in horses. The results show that carprofen was more effective than flunixin meglumine.

Objective of the study

• The study aimed at evaluating the pharmacodynamics of the analgesic action of carprofen and flunixin on horses. It sought to determine the effectiveness of these two drugs by critically examining their actions in peripheral pain inhibition.

The Methodology

• The study was designed as an open randomised cross-over trial.
• Two skin-stimulation systems i.e., the withers model and the “heating element” model were used to stimulate pain situation in the horses.
• The analgesic efficacy of the drugs was tested against a placebo, which in this case was a physiological solution of sodium chloride.

Study Findings

• In the ‘withers model’, none of the two drugs showed any analgesic effect.
• In the ‘heating element’ model, carprofen with an injected dose of 0.7mg/kg was found to inhibit the pain perception for approximately 24 hours in the horses after its injection.
• Flunixin, even with a higher injected dose of 1.1mg/kg, could not inhibit peripheral pain in the same model.

Implication of findings

• The results point out that carprofen stands better than flunixin in serving as an efficient peripheral pain reliever, as it could inhibit peripheral pain in horses at a lower concentration (0.7mg/kg) and for a longer duration (24 hours).
• The plasma concentration of carprofen needed to be at least 1.5 micrograms/ml to impart its analgesic effect, implying the importance of maintaining a particular plasma concentration to receive the desired analgesic benefits from the drug.
• The study also revealed the effectiveness of the ‘heating element’ model in demonstrating pain perception and analgesic effects as compared to the ‘withers model’.