Understanding pain pathways and pharmacologic targets (Proceedings)

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Understanding pain pathways and pharmacologic targets (Proceedings)

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Aug 01, 2011

The COX pathway

Most commonly used veterinary pain drug

          o COX-1 Not really used in veterinary Medicine
          o COX-2 Rimadyl, Metacam, Previcox and Deramaxx
• Works by stopping production of prostanoids fromprostaglandins by inhibition of the cyclooxygenase pathway.
• Prostanoids cause pain and inflammation through stimulation of PGE receptors at both the nociceptor and dorsal horn of the spinal cord
• COX Contraindications
     o Moderate to severe renal disease
     o End stage liver disease
     o Concurrent use of aspirin or corticosteroid
     o Chronic use in cats??
     o In face of gastro-intestinal signs
• COX Doses - Follow manufacturer's instructions, but try to find lowest effective dose.

Acetaminophen

• Belongs in a class of its own
• There have been many attempts to classify it. It probably works by binding to cannabinoid receptors but other possible pathways include COX, seratonin, opioid, norepinephrine and nitric oxide
• It only seems to work in some dogs, never use in cats. It is a good adjunct medicine to try out, but I would never use it by itself...not dependable enough.
• Dog Dose is 10 mg/kg q8-12h

Biphosphonates

• Good analgesic effect for patients with osteosaroma, especially those with metastatic diesease. Biphosphonates inhibit osteoclastic activitiy, thereby reducing bone resorption and they promote repair through stimulation of osteoblast differentiation and bone formation. They have poor oral absorption so are given by the IV route.
• Pamidronate is the one most commonly used, but some of the newer ones hold promise.