Adverse Effects of Mycophenolate Mofetil in Dogs with Immune-Mediated Disease

In the literature

Fukushima K, Lappin M, Legare M, Vier J. A retrospective study of adverse effects of mycophenolate mofetil administration to dogs with immune-mediated disease. J Vet Intern Med. 2021;35(5):2215-2221.

The Research ...

Immune-mediated diseases cause significant morbidity and mortality in veterinary patients.¹ Mycophenolate mofetil (MMF) is an increasingly popular immunosuppressive drug for management of immune-mediated diseases in dogs.^1,2 MMF selectively inhibits proliferation of T and B lymphocytes, resulting in broad immunosuppression.¹ Despite increasing use of MMF, studies on adverse effects in dogs are limited.

This retrospective study aimed to describe adverse effects of MMF administration in 131 dogs with immune-mediated diseases, including immune-mediated hemolytic anemia, immune-mediated thrombocytopenia, pemphigus foliaceus, and immune-mediated polyarthritis. Median starting dose was 17.5 mg/kg every 24 hours, divided into 2 doses for most dogs, and administered concurrently with other immunosuppressive medications, including prednisolone alone, prednisolone and cyclosporine, prednisolone and leflunomide, dexamethasone alone, dexamethasone and cyclosporine, cyclosporine alone, and budesonide.

Potential adverse effects were observed in 34 dogs (30%), leading to discontinuation of MMF in 20 dogs (15.3%). There was no difference in signalment or dose between patients with or without adverse effects. GI effects (eg, diarrhea, hyporexia or anorexia, vomiting) were most common and occurred in 31 dogs (24.4%). Median time to onset of GI effects was 10 days after MMF therapy was initiated. Ten dogs receiving no intervention or supportive care only (ie, metronidazole, tylosin, pre- or probiotics) showed improvement, and 2 dogs improved after being given a reduced dose of MMF with or without antibiotics. Most dogs improved within 7 days after onset of clinical signs. Hematologic adverse effects were rare; neutropenia occurred in 3 dogs, anemia occurred in 1 dog, and thrombocytopenia occurred in 1 dog. Two dogs developed skin eruptions. 

Although MMF is safe and effective in dogs with immune-mediated diseases, it is important to recognize potential adverse effects and provide intervention as needed.

... The Takeaways

Key pearls to put into practice:

• GI effects (eg, diarrhea, hyporexia or anorexia, vomiting) are the most common adverse effects of MMF administration in dogs and typically occur within 1 to 2 weeks.

• GI effects may require supportive care, reduced MMF dose, or discontinuation of MMF, but signs typically resolve within one week.

• Although hematologic adverse effects (eg, neutropenia, anemia, thrombocytopenia) are rare, monitoring of these values should be considered for patients receiving MMF.