Feline Infectious Peritonitis (FIP) is a serious and often fatal disease in cats, but recent advancements in antiviral treatments, particularly with the drug remdesivir, are offering new hope for affected animals. Although traditionally a death sentence, FIP is now increasingly manageable, with a growing number of cats achieving remission thanks to therapies like remdesivir. This is especially significant for older cats, who may be more vulnerable to the disease and its complications.
FIP is caused by a mutated form of the feline coronavirus. It manifests in two primary forms: effusive, characterized by fluid buildup in the abdomen or chest, and non-effusive, which presents with a wider range of symptoms affecting organs like the kidneys, liver, and brain. The disease was once considered universally fatal, but research and clinical experience have revealed effective treatment options, primarily focused on antiviral medications.
Remdesivir: A Key Antiviral in FIP Treatment
Remdesivir, originally developed as a treatment for Ebola and later used in humans during the COVID-19 pandemic, has demonstrated significant efficacy against FIP. The drug works by disrupting the virus’s ability to replicate, specifically targeting RNA-dependent RNA polymerase, which is crucial for viral replication [2]. Both injectable and oral formulations of remdesivir are being used, with compounded oral remdesivir becoming increasingly popular due to ease of administration [3]. A study in New Zealand showed that oral remdesivir, at a dose rate of 30 mg/kg q24h, is an effective treatment for effusive FIP [3].
However, remdesivir isn’t without potential side effects. Subcutaneous injections can be painful for cats [1]. The VCA Animal Hospitals notes that remdesivir’s employ in cats is considered “off label,” meaning it hasn’t been specifically approved by the U.S. Food and Drug Administration (FDA) for this purpose, but is commonly prescribed by veterinarians [5].
Treatment Outcomes and Considerations for Older Cats
A prospective observational study involving 29 cats with FIP found that 25 (86%) entered remission and survived beyond six months [3]. Remission was achieved within 84 days in 22 (75%) of those cats while receiving oral remdesivir. While the overall survival rate is encouraging, the study highlighted a difference in outcomes between effusive and non-effusive forms of the disease. Notably, 50% of non-effusive cases relapsed, compared to only 5% of effusive cases [3].
Older cats with FIP may present unique challenges. They are more likely to have underlying health conditions that could complicate treatment or increase the risk of side effects. The study suggests that a higher dose rate or frequency of administration of remdesivir may be necessary for non-effusive cases, and this consideration may be particularly important in older cats whose immune systems may be less robust [3].
For cats that relapse, molnupiravir was offered as a rescue therapy in the New Zealand study, demonstrating that alternative antiviral options exist when initial treatment isn’t fully successful [3]. Molnupiravir and EIDD-1931 work by inducing lethal mutations in the virus’s RNA [2].
What’s Next in FIP Research and Treatment?
Ongoing research continues to refine treatment protocols and explore new antiviral therapies for FIP. Veterinarians are similarly working to optimize monitoring protocols to detect relapse early and provide timely intervention. The increasing availability of oral remdesivir has made treatment more accessible for many cat owners, but careful veterinary supervision remains crucial. Further studies are needed to determine the optimal dosage and duration of treatment, particularly for cats with non-effusive FIP and for older cats with co-existing health issues.
If you are concerned about your cat’s health, please consult with your veterinarian for a proper diagnosis and treatment plan.
Disclaimer: This article provides informational content about feline infectious peritonitis and remdesivir treatment. It is not intended to be a substitute for professional veterinary advice, diagnosis, or treatment. Always seek the advice of your veterinarian regarding any medical condition or treatment options for your pet.
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