Feline Infectious Peritonitis

FIP Knowledge Center

Feline infectious peritonitis went from almost always fatal to treatable in a decade — on the back of one antiviral and its relatives. This is the honest, sourced version: what FIP is, how it’s treated now, what the studies actually report, and where the evidence runs out. Not a storefront.

Start: What is FIP?Treatment calculator

Articles

FIP BasicsWhat is FIP in cats? Causes, symptoms, wet vs dry, and whether it's curable nowFeline infectious peritonitis was, for decades, an almost certain death sentence. That changed. Here is what FIP actually is, how to recognise it, how it's diagnosed, and the honest state of the cure.Treatment EvidenceFIP treatment: what the current evidence actually shows (cure rates, dose, and relapse)Antiviral therapy turned FIP from fatal to curable. Here is what the published studies report — success rates, treatment length, relapse, and how oral and injectable options compare — with the numbers and their sources.SymptomsMy cat has a fever — could it be FIP? How to tell, and when to worryA fever that won't go away is one of the most common early signs of FIP — but most feverish cats do not have FIP. Here's how to read the difference, the red flags that raise suspicion, and what to ask your vet.SymptomsDry (non-effusive) FIP symptoms: the quiet form that's easy to missDry FIP produces no fluid buildup, so it lacks the obvious swollen belly of the wet form. That makes its signs vaguer and slower — persistent fever, weight loss, and clues that depend on which organs are affected.SymptomsOcular FIP: the eye symptoms, and why they change treatmentFIP can show up in the eyes — a change in iris colour, cloudiness, or inflammation inside the eye — sometimes as the first or only obvious sign. It matters because the antiviral has to reach the eye, which means a higher dose.SymptomsNeurological FIP: symptoms, what it means, and whether it's still treatableNeurological FIP is when the virus reaches the brain and spinal cord — wobbliness, tremors, seizures, or a change in behaviour. It's the hardest form to treat because the drug must cross into the brain, but it is still treatable at the right dose.Treatment EvidenceOral vs injectable FIP treatment: what the evidence saysFor years FIP meant daily injections. Oral antivirals changed that. Here's how oral and injectable options compare on effectiveness, tolerability, and cost — and why many modern protocols use both.

Treatment methods

The four antivirals the modern FIP protocol is built around — how each works, what the evidence shows, and where the supply is unregulated.

TreatmentGS-441524The core antiviral — the molecule that made FIP curable TreatmentRemdesivirThe injectable prodrug of GS-441524, legal in the UK and Australia TreatmentMolnupiravir (EIDD-2801)Oral antiviral — primary or salvage option TreatmentEIDD-1931The active metabolite behind molnupiravir

Tools

CostWhat FIP treatment costsWhat an 84-day antiviral course realistically runs, and what drives the price.CalculatorFIP treatment dosage calculatorAn educational estimate of daily dose by weight and FIP form — to bring to your vet, never a prescription.

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