How Do Nonsteroidal Anti-Inflammatory Medications Work?

Most anyone who has ever owned a horse has given a dose of a nonsteroidal anti-inflammatory drug (NSAID). Commonly prescribed examples include phenylbutazone (bute) and flunixin meglumine (Banamine®, Merck Animal Health, and others). The NSAIDs effectively reduce pain and fever in horses.

Nonsteroidal anti-inflammatory drugs reduce inflammation by blocking a different enzyme pathway than steroids, another class of potent anti-inflammatory drugs. Regardless of the pathway, the end result is the production of inflammatory mediators (prostaglandins and thromboxanes). These inflammatory mediators produce the clinical signs of inflammation: pain, redness, swelling, heat, and loss of use. Most commonly used equine NSAIDs work by blocking an enzyme called cyclooxygenase, which produces prostaglandins and thromboxanes from fatty acids in the cells.

In recent years, it was recognized that there are at least three different cyclooxygenase enzymes and some of these generate end products that have beneficial effects. Some NSAIDs block cyclooxygenase enzymes and others, such as firocoxib (Equioxx®, Merial), are selective for cyclooxygenase-2 (COX-2), which produces more detrimental and inflammatory end products. Nonsteroidal anti-inflammatory drugs can cause gastrointestinal ulceration and kidney damage in dehydrated animals. It is important to administer these drugs as prescribed and directed by your veterinarian to avoid and monitor for any possible adverse effects.