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Ibuprofen, 2-(4-isobutylphenyl) propionic acid, is used for its anti-inflammatory, antipyretic, and analgesic properties in animals and humans. It is rapidly absorbed orally in dogs with peak plasma concentrations seen in 30 min to 3 hr. Presence of food can delay absorption and the time to reach peak plasma concentration. The mean elimination half-life is ~4.6 hr. Ibuprofen is metabolized in the liver to several metabolites, which are mainly excreted in the urine within 24 hr. The major metabolic pathway is via conjugation with glucuronic acid, sometimes preceded by oxidation and hydroxylation.
Ibuprofen has been recommended in dogs at 5 mg/kg. However, prolonged use at this dosage may cause gastric ulcers and perforations. GI irritation or ulceration, GI hemorrhage, and renal damage are the most commonly reported toxic effects of ibuprofen ingestion in dogs. In addition, CNS depression, hypotension, ataxia, cardiac effects, and seizures can be seen. Ibuprofen has a narrow margin of safety in dogs. Dogs dosed with ibuprofen at 8-16 mg/kg/day, PO for 30 days showed gastric ulceration or erosions, along with other clinical signs of GI disturbances. An acute single ingestion of 100-125 mg/kg can lead to vomiting, diarrhea, nausea, abdominal pain, and anorexia. Renal failure may follow dosages of 175-300 mg/kg. CNS effects (ie, seizures, ataxia, depression, coma) in addition to renal and GI signs can be seen at dosages >400 mg/kg. Dosages >600 mg/kg are potentially lethal in dogs.
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