top of page


Do you have a question not addressed here? Email us at
Are any drugs contra-indicated during antiviral treatment for FIP?

At present, there are no known drug interactions with GS-441524, Remdesivir, GC376 or Molnupiravir.  For Remdesivir, it has been noted in humans that concurrent treatment with chloroquine, hydroxychloroquine is not recommended.

If additional medications are required concurrent with antiviral administration, especially at the beginning of treatment, it may be wise to prefer drugs that do not have known neurological side effects so as to not cloud the diagnostic picture.

Immune-suppressive drugs, such as corticosteroids should be avoided when possible so as to prevent impairment of the immune response.  While such drugs may be temporarily helpful to stabilize a patient, they should be discontinued as early as is possible without compromising patient stability.

I've heard that flea treatment is not recommended during treatment.  Is that so?

There is no scientific evidence that usage of flea treatment compromises the effectiveness of treatment with GS-441524 or other antivirals used to treat FIP.  There is also no scientific evidence that usage of flea treatment during treatment causes greater risk.

Flea treatments do have the possibility of neurological or other side effects which could cloud the diagnostic picture, so it is preferable to use a product that the cat has successfully used in the past without issue.  However for a stable patient there is no contraindication to using flea control medication.  As with any medication the benefits and risks should be weighed.

Should cats diagnosed with FIP be quarantined?

It is not considered necessary to quarantine a cat who has been diagnosed with FIP  as horizontal transmission of the mutated FIP virus is considered extremely uncommon, if it happens at all.  Studies have confirmed that even in cases where cats in close contact with each other developed FIP, the virus mutated independently from FECV within each cat rather than horizontal transmission of the mutated FIP virus.

That said, research has shown that FIPV is present in the feces of some cats with FIP, which does make horizontal transmission theoretically possible.  Additionally, research has also shown that even when the mutated virus is shed, it does not seem very contagious.

Recent research has supported a "circulating virulent–avirulent FCoV" theory (as opposed to horizontal transmission) as an explanation for clusters of cases sometimes seen in multi-cat environments, particularly shelters, catteries and rescues.

Have there been recurrences of FIP in treated cats beyond the 3 month "observation" period?

A small number of cats who had been treated for FIP have been reported as re-diagnosed with FIP as much as 1-2 years beyond the end of their FIP treament.  It is unknown if these recurrences represent a delayed relapse of the original disease, or if the virus again independently mutated to FIP from FECV.

The incidence of this seems extremely small -- only tens of reports of this have surfaced out of many thousands of cats successfully treated.

Are there recommendations for pregnant cats who have been diagnosed with FIP?

Dr. Pedersen has published a great article on this at

Is it safe to vaccinate a cat during treatment?  What about during the 3 month observation period?

Typically, routine vaccinations for cats during antiviral treatment for FIP is discouraged unless the cat is unvaccinated (or of questionable vaccine status) and is at risk of exposure to disease.  For example, it may be wise to give FVRCP vaccines unvaccinated kittens in a rescue setting, even during treatment for FIP.

Once treatment has ended there is no reason that a cat cannot be vaccinated, including during the 3 month "observation period" following treatment.  As a practical matter however, since relapses are more likely to reveal themselves in the first few weeks following cessation of treatment, it may be wise to avoid vaccines immediately following treatment simply to prevent confusion of any vaccine reaction or stress reaction with an FIP relapse.

Can a cat undergoing FIP treatment be spayed/neutered?  What about other surgeries?

Spaying/neutering a cat during the latter part of FIP treatment is a relatively common practice, typically done around weeks 9-10. This may in fact be preferable to waiting until after treatment.  since going into heat is stressful on the cat (and owner!) and may impair their recovery against FIP.  

Provided that the cat is stable and has shown favorable response to treatment, other surgeries can be performed when necessary.  Care should be taken to conduct the surgery and recovery period in the least stressful protocol and logistics possible.

I've heard a vaccine exists for FIP, is it recommended?

A vaccine for FIP does exist, however it is generally not recommended for use as there is not sufficient evidence that it confers a clinically relevant level of protection.

What are the recommendations for treatment or monitoring for the 3 month observation period following FIP antiviral treatment?  

The 3 months following the end of FIP treatment are intended to confirm whether or not the treatment has been successful in eliminating the FIP virus -- or not. Once the decision has been made to discontinue treatment, the antiviral therapy should simply be discontinued  -- no tapering is necessary.   No additional treatment or supplementation is needed during this time unless a relapse occurs.


Many cats continue getting a CBC and chemistry panel every 4-6 weeks during the observation period, but this is not strictly necessary -- monitoring for signs of disease is usually sufficient.

In general, the cat can be treated as one would a normal cat-- surgeries, treatments for other diseases or conditions, etc. can be conducted as usual.  However, given that relapses most commonly reveal themselves during the first month after  treatment is ended, it may be wise to avoid anything during this time that could complicate identifying or treating a relapse.

bottom of page