Methemoglobinemia associated with dermal application of benzocaine cream in a cat.

Benzocaine, an ester-type local anesthetic, was believed responsible for apparent methemoglobinemia in a cat. The cat was admitted with acute respiratory distress, vomiting, and collapse, which began 15 to 20 minutes after topical application of the drug. Treatment consisted of supportive therapy and intravenous administration of methylene blue. The respiratory rate improved within 5 to 10 minutes of methylene blue administration and continued over a period of 2 hours. Benzocaine-induced methemoglobinemia has been reported in man, dogs, and cats. This report supports the findings of others regarding the potential toxicity of topical ester-type local anesthetics.