title: Methylene blue can be used to treat methemoglobinemia in cats without inducing Heinz body hemolytic anemia.
abstract: Methylene blue (MB) is the drug of choice in the treatment of methemoglobinemia (MTHB) in humans and most domesticated animals, but is reported contraindicated in cats. Although prolonged treatment of cats for urologic syndromes with MB-containing antiseptics causes Heinz body (HB) hemolytic anemia, there is no evidence to suggest that single or repeated therapeutic doses of MB cause hemolytic anemia. We investigated the efficacy and safety of MB in reversing nitrite-induced MTHB in cats. Forty random-bred adult cats (20 males and 20 females) were divided as follows: Group 1, 1.5 mL saline/kg bw iv (control); Group 2, 1 dose of 1.5 mg MB/kg bw iv; Group 3, 2 doses of 1.5 mg MB/kg bw iv 4 h apart; Group 4 1 dose of 1.5 mg sodium nitrite/kg bw iv; Group 5, 1 dose of 1.5 mg sodium nitrite/kg bw iv followed by 1 dose of 1.5 mg MB/kg bw iv 1 h later; and Group 6, 1.5 mg sodium nitrite/kg bw iv followed in 2 h by 2 doses of 1.5 mg MB/kg iv 4 h apart. One iv dose of MB sufficiently and rapidly reversed MTHB in the cats without increasing circulating HB-containing red blood cells. Giving 2 iv doses of MB without or after sodium nitrite significantly increased the frequency of circulating HB-containing red blood cells. Pre-exposure to sodium nitrite potentiated the HB-inducing effect of 2 doses of MB. Hemolytic anemia was not observed or demonstrated in any of the cats groups.
authors.affiliation: Comparative Toxicology Laboratories, Kansas State University, Manhattan, KS 66506-5606.
authors.forename: W K
authors.initials: WK
authors.lastname: Rumbeiha
authors.forename: F W
authors.initials: FW
authors.lastname: Oehme
mesh_terms: D000743:Anemia, Hemolytic / Q000139:chemically induced / Q000662:veterinary*; D000818:Animals; D002371:Cat Diseases / Q000139:chemically induced / Q000188:drug therapy*; D002415:Cats; D000075202:Contraindications; D004906:Erythrocyte Count / Q000662:veterinary; D005260:Female; D006366:Heinz Bodies / Q000187:drug effects*; D006400:Hematocrit / Q000662:veterinary; D006454:Hemoglobins / Q000032:analysis; D008297:Male; D008708:Methemoglobinemia / Q000188:drug therapy / Q000662:veterinary*; D008751:Methylene Blue / Q000009:adverse effects / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D006454:Hemoglobins; D008751:Methylene Blue