ORIGINAL RESEARCH article
Front. Vet. Sci.
Sec. Comparative and Clinical Medicine
Hematologic follow-up of metamizole-associated Heinz body anemia in dogs
1. LMU Small Animal Clinic, Ludwig-Maximilians-University Munich, Munich, Germany
2. DEXX Laboratories, Kornwestheim, Germany
Select one of your emails
You have multiple emails registered with Frontiers:
Notify me on publication
Please enter your email address:
If you already have an account, please login
You don't have a Frontiers account ? You can register here
Abstract
IAbstract Introduction: Heinz body (HB) anemia is uncommon in dogs. Metamizole is described as a potential trigger in isolated cases. Aim of the study: The present study describes the course of metamizole-associated HB anemia in dogs with the development of hematocrit, HBs, and eccentrocytes. In addition, the correlation between HBs, eccentrocytes, hematocrit, and reticulocytes is investigated. Materials and methods: In this prospective observational study, 25 dogs with metamizole-associated HB anemia were included. Hematologic examinations and blood smear evaluations for quantification of HBs and eccentrocytes (stained with brilliant cresyl blue and modified Wright’s stain) were performed on day 0 and at the control intervals 1–3, 4–6, 7–13, and 14–20 days after discontinuation of metamizole and initiation of antioxidant treatment. Known alternative causes of oxidative erythrocyte damage were excluded. Data were analyzed using Kruskal-Wallis test, Friedman test, and Spearman correlation. Results: HB anemia was detected a median of 10 days after initiation of metamizole (median cumulative dose 720 mg/kg). On day 0, HB percentage did not correlate with metamizole dose or hematocrit. The eccentrocyte count did not correlate with metamizole dose, hematocrit, or reticulocyte count. However, a moderate to strong correlation was identified between HB percentage and reticulocyte count (r = 0.630). Median HBs and eccentrocytes decreased from 26.5% and 2.6% on day 0 to 1.3% and 0% on days 14–20, while median hematocrit increased from 24% to 33%. Four dogs received blood transfusions. All patients had at least one concurrent disease. Twenty-one dogs survived and four dogs were euthanized or died. Conclusion: In dogs with concurrent disease, metamizole administration may be associated with clinically relevant erythrocyte oxidative damage. Discontinuation of metamizole and initiation of antioxidant therapy were followed by a decrease in HBs and recovery of hematocrit. The use of metamizole in multimorbid dogs should be carefully considered and accompanied by regular hematology controls.
Summary
Keywords
diyrone, drug-associated hematotoxicity, eccentrocytes, erythrocyte, Hemolysis, Oxidative Stress
Received
19 June 2026
Accepted
03 August 2026
Copyright
© 2026 Richter, Geisen, Palic and Doerfelt. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Vera Geisen
Disclaimer
All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.