Analgesia.

The research article reviews different methods of relieving pain in horses, with a primary focus on pharmacological approaches categorized into three primary strategies—opioid receptors, alpha 2 receptors, and drugs that reduce prostaglandin synthesis. These approaches are tailored based on factors such as pain source, therapy duration, need for sedation, and potential side effects.

Pharmacological strategies for pain relief

• The article discusses three primary pharmacological strategies for relieving animal pain, especially in horses. These methods are aimed at different areas in the Central Nervous System (CNS) such as peripheral nociceptors, primary and secondary spinal neurons, and pain-processing areas.
• The first strategy is drugs binding and activating opioid receptors – opioids and alpha 2 agonists are particularly effective for visceral (internal organs) pain associated with colic in horses. It mentions that among such drugs, Butorphanol is commercially available and provides visceral analgesia of much higher effectiveness than pentazocine or flunixin meglumine, but not more than the alpha 2 agonists.
• The second strategy uses drugs that interact with alpha 2 receptors. One major consideration when using either opioids or alpha 2 agonists is their potential side effects—the sedative impact of alpha 2 agonists and increased locomotion and CNS excitability caused by certain opioids.
• The third strategy is drugs designed to reduce de novo prostaglandin synthesis. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are often used here, particularly for pain associated with inflammation or endotoxemia (toxins in the blood). These drugs provide prolonged pain relief and can suppress the effects of endotoxin. They are also widely used for long-term therapy of musculoskeletal diseases.

Considering NSAIDs for Equine Pain Management

• The paper mentions that despite the availability of many NSAIDS in approved equine formulations (such as phenylbutazone, meclofenamic acid, flunixin meglumine, and naproxen for oral use), practitioners should note the differences among them when selecting an analgesic. These differences are in their ability to reduce fever (ameliorate pyrexia), affect platelet function, alleviate pain, and reduce inflammation.
• The article notes that all NSAIDs have the potential to cause ulcers (ulcerogenic). Therefore, horses that do not tolerate a particular NSAID may need to be switched to another that is better tolerated, or else to a drug from a different analgesic class. This highlights the importance of careful selection and monitoring when using NSAIDs for pain relief in horses.