Toxicology Brief: Naproxen toxicosis in dogs - Veterinary Medicine
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Toxicology Brief: Naproxen toxicosis in dogs
At high doses, naproxen, an NSAID commonly found in our medicine cabinets, can be harmful in dogs. Be prepared to recognize and treat this toxicosis in your canine patients.


VETERINARY MEDICINE


DECONTAMINATION

Decontamination may not be required for a dose less than 7 mg/kg in a dog but may decrease the risk of GI irritation. If ingestion of naproxen was recent (less than two hours) and the patient shows no clinical signs, emesis can be induced by using apomorphine (0.03 mg/kg intravenously; or, in the conjunctival sac, 0.25 mg/kg after dissolving the tablet in saline solution) or 3% hydrogen peroxide (2 ml/kg orally with a maximum of 50 ml). If emesis is unproductive, consider using activated charcoal (1 to 3 g/kg orally).2

If the patient exhibits no clinical signs and the ingestion occurred more than two hours before evaluation, consider administering activated charcoal (1 to 3 g/kg orally). The first dose of activated charcoal should be administered with a cathartic. However, with repeat doses of activated charcoal, a cathartic should not be used, particularly if the patient is dehydrated or has diarrhea.10

In dogs with ingestions of naproxen greater than 13 mg/kg, an initial dosage of activated charcoal (1 to 3 g/kg orally) may be followed with half the original amount every six to eight hours for 24 to 48 hours after ingestion to interrupt any enterohepatic recirculation.

MONITORING AND TREATMENT

Monitor the serum sodium concentration regularly if activated charcoal is given because administration of activated charcoal may be associated with hypernatremia.10 Hypernatremia may manifest clinically as muscle fasiculations, tremors, and seizures. If the patient is not vomiting, allow access to water.11 If hypernatremia develops, the APCC recommends warm-water enemas in addition to administration of appropriate intravenous fluids to lower the serum sodium concentration and decrease resultant adverse effects to the central nervous system.12

Monitor for signs of GI irritation and ulceration, and initiate GI protection by using a combination of sucralfate (0.5 to 1 g orally t.i.d.), misoprostol (2 to 5 μg/kg orally every 8 to 12 hours), and famotidine (0.1 to 0.2 mg/kg orally, subcutaneously, intramuscularly, or intravenously b.i.d.) or omeprazole (0.5 to 1 mg/kg orally once a day).2 Continue administering GI-protective medications for at least seven to 14 days because of the long half-life of naproxen in dogs. Control vomiting with antiemetics as needed.12 If severe gastric ulceration develops, colloid therapy or blood transfusions may be needed.4

For dosages at which adverse renal effects are possible, obtain a baseline serum chemistry profile, a complete blood count, and a urinalysis including a urine specific gravity before initiating fluid diuresis. Repeat a renal panel (BUN and serum creatinine and electrolyte concentrations) at 24, 48, and 72 hours. Repeat the complete blood count and urinalysis if indicated. Initiate intravenous fluid diuresis. Because of the long half-life of naproxen in dogs, the APCC recommends twice maintenance fluids for at least 72 hours. If results of the renal panel are within the reference range 72 hours later, gradually decrease the rate of fluid administration over the next 24 hours.

Increased liver enzyme activity has been reported subsequent to NSAID exposure in people4 and after naproxen intoxication in dogs.6 Monitor liver enzyme function and initiate liver-protective medications if marked elevations in liver enzyme activity develop. S-adenosyl-methionine (SAMe) (20 mg/kg orally once daily2) may be administered.

PROGNOSIS

Gastrointestinal irritation or ulceration typically resolves with appropriate treatment. Patients that develop GI ulceration are at risk for GI perforation and death from GI bleeding or sepsis. Renal effects of NSAIDs generally are considered reversible if they are discovered early and treated aggressively.12 Patients with underlying GI or renal disease are more at risk, as are patients that receive medications that interact with NSAIDs.

Camille DeClementi, VMD, DABT, DABVT, ASPCA Animal Poison Control Center, 1717 S. Philo Road, Suite 36, Urbana, IL 61802


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Source: VETERINARY MEDICINE,
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