Heinz Body Hemolytic Anemia Associated with the Use of Urinary Antiseptics Containing Methylene Blue in the Cat

Abstract

SUMMARY Hemolytic anemia developed in 6 cats after the oral administration of either of 2 similar antiseptic-antispasmodic preparations commercially available for the treatment of cystitis and urolithiasis. The anemia was believed to be caused by the methylene blue contained in these preparations and was characterized by the formation of Heinz body inclusions within mature erythrocytes. The degree of anemia was variable but frequently was such that death probably would have ensued without supportive therapy. The variability in the degree of anemia resulting from use of commercial preparations was believed to be related to differences in the rate of their absorption from the gastrointestinal tract. Within a few days after methylene blue was given to 2 cats in an amount equivalent to that contained in the recommended dosage of the commercial preparations, a severe hemolytic crisis developed that required blood transfusions to prevent impending death. A limited number of erythrocyte enzyme determinations and a thermolabile screening test for abnormal hemoglobin were performed in an attempt to determine the cause of the excessive Heinz body formation and the hemolytic anemia. Specific defects or deficiencies could not be found. It was concluded that the administration of methylene blue to cats can cause Heinz body hemolytic anemia, the course and severity of which are unpredictable when enteric-coated combination products are given.