A common application of NSAIDs is the management of osteoarthritis (OA). Because OA is characterized by both chronic and acute flare-ups of pain and inflammation secondary to joint pathology, the analgesic and anti-inflammatory properties of NSAIDs can be helpful with intermittent or continuous therapy.1,2 Numerous NSAIDs (eg, carprofen, meloxicam, firocoxib, deracoxib, grapiprant) are labeled for management of OA in dogs; however, no NSAIDs are currently FDA-approved for long-term use in cats.
Although NSAIDs are typically well-tolerated in veterinary patients, sustained use to treat OA in older patients warrants close monitoring for potential adverse effects in the GI tract, kidneys, and liver. GI adverse effects have been linked to a variety of mechanisms (eg, direct irritation of the GI mucosa, inhibition of prostaglandin E2) and potentially include ulceration, gastritis, enteritis, and perforation.3 COX expression in the kidneys can lead to production of prostaglandins, which help maintain renal homeostasis by affecting renal blood flow and glomerular filtration rate, among other functions.4 Thus, use of NSAIDs in dogs may exacerbate underlying chronic kidney disease or lead to acute kidney injury, reversible renal insufficiency, or papillary necrosis.5-8
Adverse effects in the liver are uncommon and can be attributed to idiosyncratic reactions.9 Hepatopathy has been suggested or documented with NSAID use.10-15 Idiosyncratic hepatotoxicity that occurs with carprofen administration typically involves acute hepatic necrosis, and signs of toxicosis (eg, marked increase in serum ALT) usually occur ≈2 to 4 weeks after initiation of carprofen.11
In patients receiving long-term NSAID therapy, baseline laboratory work, (ie, patient hematocrit, liver enzymes, kidney values, and urinalysis) should be performed to help determine whether the patient has underlying renal or hepatic dysfunction. In addition, ongoing clinical monitoring of renal and hepatic parameters is recommended, and the pet owner should monitor for evidence of GI intolerance (eg, inappetence, vomiting, diarrhea, melena) at home. The authors recommend blood work be rechecked ≈2 to 4 weeks after initiation of NSAID treatment, then every 3 to 6 months. In patients that develop adverse effects while receiving an NSAID, the drug should be stopped and laboratory work (minimum CBC and serum chemistry profile) repeated to assess for possible drug toxicity.