Immunosuppressive Therapy for Feline Non-Regenerative Anemia

Primary bone marrow disorders associated with feline non-regenerative anemia can be challenging to treat. Available treatment information is limited, and responses vary according to the underlying disorder. Glucocorticoids form the foundation of immunosuppressive treatment, while additional agents may be considered in selected cases. 

Glucocorticoids as the Initial Immunosuppressive Option 

Glucocorticoids are used widely in cats with primary medullary disease because of their anti-inflammatory and immunosuppressive effects. A significant proportion of cats with pure red cell aplasia (PRCA) and non-regenerative immune-mediated hemolytic anemia (NRIMHA) respond to glucocorticoid monotherapy, although response is more variable with other bone marrow disorders^1,2,3. 

The reported dosages include prednisone/prednisolone at 2–4 mg/kg PO q24h or 1–2 mg/kg PO q12h^1,2. 

Ciclosporin 

Ciclosporin is one of the most widely used adjuncts to, or substitutes for, glucocorticoid therapy in feline primary medullary disease. It has been used in cats with NRIMHA, PRCA and myelodysplastic syndromes^1,3,4. 

The reported feline oral microemulsion formulation reaches steady state after approximately seven days at the labeled dosage. However, doses required to achieve clinical remission in PRCA cases have tended to be higher than the labeled dose, with clinical remission reported after 2–7 weeks^4,5. 

Reported dosing for ciclosporin is 5–20 mg/kg PO q24h⁴. 

Gastrointestinal adverse effects are among the most common concerns and include vomiting, hypersalivation, diarrhea, weight loss, regurgitation, and lethargy. Secondary infections, including toxoplasmosis and salmonellosis, have also been reported^2,4,6,7. Less common concerns include anaphylaxis during intravenous administration and hepatotoxicity. Long-term administration has also been associated with reported malignancy, particularly lymphoma². 

Compounded transdermal ciclosporin is not recommended because absorption is inconsistent². 

Chlorambucil 

Chlorambucil has been used as an adjunct to glucocorticoid therapy in a limited number of cats with NRIMHA.5,81 Reported adverse effects include myelosuppression, hepatopathy, Fanconi syndrome, and myoclonus^2,7. 

The reported dose is 2 mg/cat PO q48h. Compounded chlorambucil suspension also has limited stability, which may make routine use impractical². 

Mycophenolate Mofetil 

Mycophenolate mofetil may be considered for NRIMHA, PRCA, or aplastic anemia. However, blood concentrations can be variable and unpredictable, creating a risk of over- or under-dosing without monitoring. Gastrointestinal adverse effects appear to be dose-related and self-limiting². 

Reported dosing includes 10 mg/kg PO q12h, with additional intravenous and oral protocols described for short-term administration². 

Cytosine Arabinoside and Vitamin K2² 

Cytosine arabinoside has been used in feline myelodysplastic syndromes and myelofibrosis. The reported dosage for these marrow disorders is lower than that used for some other indications and is administered by subcutaneous injection daily. 

A vitamin K2 analog, menatetrenone, has also been reported as beneficial in feline myelodysplastic syndromes at 2 mg/kg, although the optimal feline dosage has not been determined. 

Avoid Azathioprine in Cats 

Azathioprine is not recommended in feline patients, and a safe dose has not been established. Cats have lower erythrocyte thiopurine methyltransferase activity than dogs and humans, which may contribute to severe neutropenia and other adverse effects associated with azathioprine administration². 

Practical Clinical Takeaway 

Immunosuppressive therapy should be selected according to the suspected or confirmed marrow disorder, with response and adverse effects monitored throughout treatment. Glucocorticoids may be effective in PRCA and NRIMHA, while ciclosporin and other agents can serve as adjunctive or alternative therapies in selected cases. The available dosing and safety information should be interpreted in the context of the individual cat rather than treated as a universal protocol. 

References 

1. Black V, Adamantos S, Barfield D, Tasker S. Feline non-regenerative immune-mediated anaemia: features and outcome in 15 cases. Journal of feline medicine and surgery. 2016 Aug;18(8):597-602. https://journals.sagepub.com/doi/pdf/10.1177/1098612X15588800 

2. Winzelberg Olson S, Hohenhaus AE. Feline non-regenerative anemia: Diagnostic and treatment recommendations. Journal of feline medicine and surgery. 2019 Jul;21(7):615-31. https://journals.sagepub.com/doi/pdf/10.1177/1098612X19856178 

3. Swann JW, Szladovits B, Glanemann B. Demographic characteristics, survival and prognostic factors for mortality in cats with primary immune-mediated hemolytic anemia. Journal of veterinary internal medicine. 2016 Jan;30(1):147-56. https://academic.oup.com/jvim/article-pdf/30/1/147/66689783/jvim13658.pdf 

4. Viviano KR, Webb JL. Clinical use of cyclosporine as an adjunctive therapy in the management of feline idiopathic pure red cell aplasia. Journal of Feline Medicine and Surgery. 2011 Dec;13(12):885-95. https://journals.sagepub.com/doi/pdf/10.1016/j.jfms.2011.07.007 

5. Roberts ES, Vanlare KA, Strehlau G, Peyrou M, Roycroft LM, King S. Safety, tolerability, and pharmacokinetics of 6‐month daily dosing of an oral formulation of cyclosporine (ATOPICA for cats®) in cats. Journal of veterinary pharmacology and therapeutics. 2014 Apr;37(2):161-8. https://onlinelibrary.wiley.com/doi/pdf/10.1111/jvp.12081 

6. Callegari C, Palermo G, Greco MF, Corrente M, Piseddu E, Auriemma E, Zini E. Pneumonia associated with Salmonella spp. infection in a cat receiving cyclosporine. Schweiz Arch Tierheilkd. 2014 Oct 1;156(10):499-503. https://sat.gstsvs.ch/fileadmin/media/pdf/archive/2014/10/SAT156100499.pdf 

7. Lappin MR, VanLare KA, Seewald W, Roycroft LM, Scorza AV, King S, Roberts ES. Effect of oral administration of cyclosporine on Toxoplasma gondii infection status of cats. American journal of veterinary research. 2015 Apr 1;76(4):351-7. https://www.academia.edu/download/95214243/ajvr.76.4.351.pdf 

8. Reinert NC, Feldman DG. Acquired Fanconi syndrome in four cats treated with chlorambucil. Journal of feline medicine and surgery. 2016 Dec;18(12):1034-40. https://journals.sagepub.com/doi/pdf/10.1177/1098612x15593108