Nonsteroidal Antiinflammatory Drug Toxicosis

Nonsteroidal Antiinflammatory Drug Toxicosis



Basic Information image



Definition




• Adverse effects of the nonsteroidal antiinflammatory drugs (NSAIDs) are caused by cyclooxygenase (COX) inhibition in tissues where prostaglandins are beneficial and protective.


• Renal papillary necrosis (medullary crest necrosis), oral and gastrointestinal (GI) ulceration, and right dorsal colitis are common signs of NSAID toxicity in horses.


• Platelet aggregation is classically inhibited by NSAIDs that prevent thromboxane production via the COX-1 pathway.



Epidemiology



Species, Age, Sex


Neonates and geriatrics are more at risk.



Risk Factors


Renal insufficiency, dehydration, concurrent use of both phenylbutazone and flunixin meglumine, concurrent nephrotoxic drug therapy (eg, aminoglycosides), and history of previous NSAID toxicity



Clinical Presentation



History, Chief Complaint




• NSAID administered


image NSAIDs approved for use in horses include aspirin, flunixin meglumine (Banamine, generics), ketoprofen (Ketofen, Anafen), diclofenac (topical, Surpass), phenylbutazone (generics), firocoxib (Equioxx), meclofenamic acid (Arquel), and vedaprofen (Quadrisol, Canada and Europe).

image The highest incidence of toxicity is associated with phenylbutazone administration.

• Amount administered: Phenylbutazone may cause toxicity when administered according to the label dose. Other NSAIDs usually require an overdose to cause toxicity.



Physical Exam Findings




• Colic


• Anorexia


• Poor body condition


• Diarrhea


• Oral mucosal erosions, odontoprisis, sialism


• Regurgitation of milk and pain after nursing in foals


• Oliguria



Etiology and Pathophysiology




• Nephrotoxicity: NSAIDs typically have little effect on renal function in normal adult animals, but they decrease renal blood flow and glomerular filtration rate in patients with congestive heart failure, those that are hypotensive or hypovolemic (especially during anesthesia and surgery), and those that have chronic renal disease. Renal papillary necrosis is a severe dose-dependent toxicity most commonly associated with phenylbutazone. Although attributed to impaired renal blood flow, other mechanisms such as direct nephrotoxicity of the drug or its metabolites may be involved.


• GI toxicity: Reduced prostaglandin (PG) concentrations in the large colon may decrease colonic blood flow, resulting in mucosal atrophy, protein loss, ulceration, and inflammation.



Diagnosis image



Differential Diagnosis




• Stress-induced gastric ulceration


• Inflammatory bowel disease


• Other toxin-induced renal failure (eg, cantharidin)



Initial Database




• In asymptomatic horses, consider obtaining baseline renal and hepatic function tests.


• In symptomatic horses, monitor:


image Complete blood count and serum chemistries for anemia, neutrophilia or neutropenia, hypoproteinemia, hypoalbuminemia, hypocalcemia, and elevated liver enzymes

image Arterial blood gases for metabolic acidosis

image Renal function tests for azotemia, increased urine γ-glutamyl transferase (GGT), and increased urine GGT/urine creatinine ratio
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Jul 24, 2016 | Posted by in SMALL ANIMAL | Comments Off on Nonsteroidal Antiinflammatory Drug Toxicosis

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