Large Animal NSAIDs and Pain Management

Specific Drug Profiles

• Phenylbutazone: Often referred to as "Bute," it is a mainstay for musculoskeletal issues. However, improper administration (such as IV injection errors) can lead to severe complications like skin sloughing and thrombosis.
• Flunixin meglumine: Highly effective for both musculoskeletal pain and visceral pain (such as colic). It is also used to manage pyrexia.
• Ketoprofen: Used for musculoskeletal inflammation. In cattle (where approved in certain regions), it is used as an adjunctive therapy for fever and inflammation associated with mastitis.
• Aspirin: While widely used in humans, in horses it is primarily used for its antithrombotic action (10-20 mg/kg q 24-48h) to treat conditions like laminitis or thromboembolic colic.

Managing Colic

Colic treatment is a complex challenge that often requires a combination approach to address pain, inflammation, and endotoxemia.

Livestock Management: Cattle and Swine

Pain management in livestock presents significant hurdles. Unlike horses or companion animals, cattle do not overtly show pain, and there is often a lack of direct economic gain from treating pain alone. Furthermore, no analgesic drug is specifically approved for the sole purpose of alleviating pain in livestock; instead, drugs are used to treat specific conditions like respiratory disease or mastitis.

Indications and Use in Cattle

In cattle, NSAIDs are frequently used to manage:

1. Pyrexia (Fever): Often associated with Respiratory Disease (BRD).
2. Mastitis: Inflammation of the mammary gland.
3. Foot Rot: A painful inflammatory condition.

Dosage and Regulatory Constraints

When treating livestock, veterinarians must strictly adhere to Withhold Times (the period between the last dose and when the animal can be slaughtered for meat or milk) to ensure food safety.

Exam Tip: Always check the specific drug label for withhold times. For example, Flunixin meglumine in cattle has a meat withdrawal of 4 days and a milk withdrawal of 36 hours.

Pain Management Challenges and Adverse Effects

Regardless of species, NSAID therapy carries risks. Common side effects include gastrointestinal issues (vomiting, diarrhea, or even bleeding ulcers), changes in appetite, and potential kidney or liver damage.

Key Risks to Monitor:

• Gastrointestinal: Ulcers in the stomach or intestines.
• Renal (Kidney): Dehydrated animals are at high risk; NSAIDs can cause a loss of medullary perfusion, leading to Acute Kidney Injury (AKI).
• Improper Administration: For example, improper IV administration of Phenylbutazone can cause skin sloughing.
• Infection Risk: Improper administration of Flunixin can be associated with clostridial myositis.

Clinical Caution: In cats, NSAIDs are particularly dangerous due to slow metabolism and a higher risk of acute renal failure. Never use human medications like Acetaminophen in cats, as it is fatal.