Feline Infectious Peritonitis (FIP): an in-depth look.

endFIP attention please Please note: this section is intended for individuals who want to learn more and have a deeper understanding of feline coronavirus and FIP. Basic knowledge of veterinary/scientific terms is needed to fully comprehend this section which was created for information purposes ONLY.
If you are a veterinarian, veterinary student, vet tech or hold any other type of position in the veterinary field, please visit Dr. Diane D. Addie’s website catvirus.com.
If you are a pet parent with a sick cat, please consult a qualified veterinarian IMMEDIATELY.

The authors exclude all liability whatsoever for any loss or damage arising out of the use of this website or reliance upon its content and STRONGLY advises anybody with veterinary-related questions to consult a qualified veterinarian. No responsibility can be accepted.


Before treating the cat, it is absolutely essential that every effort has been made to ensure a correct diagnosis. Since FIP is an immune-mediated disease, treatment is directed at suppressing the inappropriate immune response, usually using corticosteroids, which could be disastrous in a lookalike condition of infectious etiology (i.e. septic peritonitis or pleurisy).

Prior to even considering treatment for feline infectious peritonitis (FIP) you absolutely MUST ensure that the cat really does have FIP.
At time of writing, FIP treatment is mainly immunosuppressive and immunosuppression of a cat with an infection other than FIP will kill the cat.

Although effusive and non-effusive FIP are not distinct diseases but rather are gradations of the same process, at time of writing there are two protocols for FIP treatment. For complete details click here.

Because FIP is an immune-mediated disease, the treatment falls into two categories: Direct action against the virus itself and modulation of the immune response.

Antiviral drugs:

The most commonly available antiviral drugs for treating FIP are either feline recombinant interferon omega (Virbagen Omega, Virbac) or human interferon. Since the action of interferon is species-specific, feline interferon is more efficacious than human interferon.

An experimental antiviral drug called GC376 was used in a field trial of 20 cats: 7 cats went into remission, 13 cats responded initially but relapsed and were euthanized. [13] This drug is not yet commercially available. Another experimental anti-viral drug called GS 441524 showed more promising results but is not commercially available either. 

Modulation of the immune response:

The most commonly used anti-inflammatory/immunosuppressant drug to treat FIP is Prednisolone.

Polyprenyl Immunostimulant (PPI) manufactured by Sass & Sass and tested by Dr. Legendre [16] [17] is the go-to drug to treat non-effusive FIP. PPI is USDA approved for the treatment of FRV and is used off-label for FIP. Its efficacy as a treatment for effusive (wet) FIP has not been demonstrated. There are many anecdotal and well-documented reports of cats treated with PPI surviving months and years after diagnosis of FIP.

In wet FIP cases, the first step to treat the cat is: Draw the effusion! Abdomino or thoraco-centesis will also remove virus-infected cells which are a source of pro-inflammatory cytokines. In addition, drawing off the effusion will immediately make the cat more comfortable, especially in thoracic effusive FIP where the cat will be able to breathe better.

Effusion can often be removed with minimal restraint and without sedation and should be sent for FCoV RT-PCR to a reliable laboratory to confirm the diagnosis of FIP. Only a small amount of effusion is required for RT-PCR testing: 1-2 ml in a plain tube will certainly give enough for a laboratory to come up with a result.

DISCLAIMER: The use of this website is at your own risk. This website is for information purposes ONLY, and it is NOT meant to replace a consultation with a fully qualified veterinary surgeon (veterinarian). It is NOT intended to be used to diagnose or treat any cat. The creators share their personal experiences, recommendations of treatments, foods, medications, supplements, and products for informative and educational purposes exclusively. The information in this site cannot and should not be used as a basis for diagnosis or choice of treatment. Creators and contributors exclude all liability whatsoever for any loss or damage arising out of use of this site or reliance upon its contents. Furthermore, creators and contributors strongly advise all users to always seek the advice of a qualified veterinarian and to obtain professional advice on the correct regimen for your cat and his or her particular situation. NO responsibility can be accepted.

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