Description    A spray application of a benzocaine-containing topical anesthetic to the larynx was followed by methemoglobinemia in cats and some of them developed signs such as cyanosis within 5-10 minutes of application. Methemoglobinemia has been cause by acetaminophen in cats. Topical application of benzocaine-containing creams has also caused methemoglobinemia in dogs and cats. Skunk musk was associated with heinz body anemia and methemoglobinemia in a dog. Methemoglobin causes a brown discoloration of the blood, which is most easily seen on white filter paper.
Species   Canine, Feline
Signs   Anorexia, Ataxia, Brown color, mucous membranes, Cyanosis, Dullness, Dyspnea, Inability to stand, Increased respiratory rate, Pale, Tachycardia, Trembling, Vomiting or regurgitation
References   Patton TG. Detecting Methemoglobinemia in Animals with a Drop of Blood. PLoS ONE 2016;11:e0167942 [Web Reference]
Court MH. Feline Drug Metabolism and Disposition : Pharmacokinetic Evidence for Species Differences and Molecular Mechanisms. Vet Clin North Am Small Anim Pract 2013;43:1039 [Web Reference]
Zaks KL. Heinz body anemia in a dog that had been sprayed with skunk musk. JAVMA 2005;226:1516
Knottenbelt C. Investigation of anaemia in dogs. In Pract 2001;23:306
Wilkie DA. Methemoglobinemia associated with dermal application of benzocaine cream in a cat. JAVMA 1988;192:85
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