Feline Infectious Peritonitis Treatment UK: 2026 Guide

Key takeaway: In 2026, the proven core of feline infectious peritonitis treatment in the UK is GS-441524, given either as a daily subcutaneous injection over an 84-day protocol or as part of a GS-441524 plus EIDD-1931 dual antiviral course. GS-441524 monotherapy has a 92% success rate reported by UC Davis (Pedersen, 2019), while the dual antiviral approach reported 78.3% remission in relapsed cats (Li and Cheah 2025). The right option depends on which of the four forms of FIP your cat has, so every plan belongs under your veterinarian.

Feline Infectious Peritonitis (FIP) is a serious viral disease, and until recently a diagnosis felt like the end of the road for many UK caregivers. That has changed. This guide walks you through what treatment looks like in 2026, the antiviral options available, and how the four forms of FIP shape the plan.

A cat resting comfortably at home.

What is the best feline infectious peritonitis treatment in the UK in 2026?

The best feline infectious peritonitis treatment in 2026 is antiviral therapy built around GS-441524, the nucleoside analogue at the core of modern FIP care. Evidence shows GS-441524 monotherapy achieves a 92% success rate (UC Davis, Pedersen 2019), and it is the hero ingredient behind more than 100,000+ cats treated since 2019.

For UK caregivers, treatment now comes in two main routes: daily injectable GS-441524, and oral dual antiviral therapy that pairs GS-441524 with EIDD-1931. Both run over a 12-week (84-day) framework under veterinary supervision.

The deciding factors are the form of FIP, whether your cat can reliably eat and take oral medication, and how you and your veterinarian want to monitor progress. There is no single answer for every cat, which is why matching the option to the diagnosis matters so much.

What are the four forms of Feline Infectious Peritonitis (FIP)?

Feline Infectious Peritonitis (FIP) takes four forms, wet, dry, ocular, and neurological, and each one shapes the dose and the treatment plan. Recognising the form your cat has is the first step toward the right protocol, and it mirrors the four-row dosing structure used with injectable GS-441524.

If you are still at the recognition stage, our overview of the 12 early warning symptoms of FIP can help you frame the conversation with your vet.

Wet (Effusive) Feline Infectious Peritonitis (FIP)

Wet, or effusive, FIP is the form where fluid accumulates in the abdomen or chest, often causing a swollen belly or laboured breathing. It tends to progress quickly, so timely treatment matters.

With injectable GS-441524, the catalog dose for wet FIP is 6 mg/kg once daily. This is the lowest of the four per-kilogram figures because the effusive form typically responds without needing to reach beyond the bloodstream into protected tissues.

Dry (Non-effusive) Feline Infectious Peritonitis (FIP)

Dry, or non-effusive, FIP produces little or no fluid and instead causes inflammatory lesions in organs, which can make it harder to spot early. Signs are often vaguer, such as weight loss, fever, and lethargy.

For dry FIP, the catalog dose for injectable GS-441524 is 8 mg/kg once daily. The higher figure reflects the need to reach affected tissues throughout the body.

Ocular Feline Infectious Peritonitis (FIP)

Ocular FIP affects the eyes, causing colour changes in the iris, cloudiness, or inflammation, and it signals that the virus has reached a protected site. It is often grouped clinically with the neurological form because both require higher dosing.

The catalog dose for ocular FIP with injectable GS-441524 is 10 mg/kg once daily. Your veterinarian may combine antiviral therapy with additional eye-focused monitoring.

Neurological Feline Infectious Peritonitis (FIP)

Neurological FIP affects the brain and spinal cord, producing signs such as wobbliness, seizures, or behaviour changes, and it demands the highest dosing to cross into the central nervous system. This is the most demanding form to treat.

For neurological FIP, the catalog dose for injectable GS-441524 is 10 mg/kg once daily. Close veterinary supervision is essential throughout the 84-day protocol.

How does GS-441524 treatment for FIP work?

GS-441524 treats Feline Infectious Peritonitis (FIP) by blocking the virus's ability to replicate, which allows the cat's own immune system to recover and clear the infection over a structured 84-day course. It is the single most studied antiviral in FIP care.

The standard injectable schedule is one subcutaneous injection per day, seven days a week, for 12 weeks (84 days), referenced to Pedersen et al., UC Davis (PMC6435921). Consistency matters, because skipped doses can undermine progress.

Many caregivers find the daily rhythm easier to sustain once they understand the milestones. Our GS-441524 treatment timeline explains what to expect week by week, and regular bloodwork during FIP treatment helps your vet confirm that the plan is working.

Injectable GS-441524 vs dual antiviral capsules: which FIP treatment is right?

Injectable GS-441524 is the most established route for feline FIP treatment and carries a 92% success rate from UC Davis (Pedersen, 2019), while the dual antiviral oral option pairs GS-441524 with EIDD-1931 and reported 78.3% remission in cats that had already relapsed (Li and Cheah 2025). The right choice depends on your cat's form of FIP and whether an oral or injectable route suits your situation better.

Injectables give precise, weight-matched dosing across all four forms of FIP. Dual antiviral capsules add a second nucleoside analogue and are positioned for wet and dry cases, which is one reason dual therapy is often described as the next evolution in FIP treatment.

Option	Best for	Route and schedule	Reported evidence
CureFIP™ GS-441524 Injectable (20mg/ml, 30mg/ml, 40mg/ml)	Wet, dry, ocular, and neurological FIP	1 subcutaneous injection daily, 7 days/week, 84 days	92% success rate (UC Davis, Pedersen 2019)
CURE FIP™ Dual Antiviral Oral Capsules (GS-441524 + EIDD-1931)	Wet and dry FIP	1 capsule daily, 12 weeks	78.3% remission in relapsed cats (Li and Cheah 2025)

A note on the oral dual route: some regions note it is not recommended once ocular or neurological signs are present, or if the cat cannot eat or defecate. For those cases, discuss the injectable route with your veterinarian.

If you want the deeper science behind combining two nucleoside analogues, our article on dual nucleoside analogue therapy for FIP covers the rationale and clinical considerations.

How much does FIP treatment cost in the UK?

FIP treatment cost depends on the product, your cat's weight, and the length of the 84-day protocol, and CureFIP lists its options in EUR on curefip.com. Prices are shown exactly as listed and are not converted here.

Product	Strength	Volume	Price
CureFIP™ GS-441524 Injectable 20mg/ml	20 mg/ml	8ml, 10ml	€79.00
CureFIP™ GS-441524 Injectable 30mg/ml	30 mg/ml	8ml, 10ml	€89.00
Cure FIP Antiviral 40mg/ml	40 mg/ml	8ml, 10ml	€119.00
CURE FIP™ Dual Antiviral Oral Capsules	GS-441524 + EIDD-1931	per catalog	€179.00
EIDD-1931 Oral Capsules	15 mg per capsule	60 per bottle	€69.00

Because total cost scales with your cat's weight and dose, ask your veterinarian to estimate how many vials or bottles the full course will require. Higher concentrations such as 30mg/ml and 40mg/ml can mean a smaller injection volume for larger cats.

What are the dual antiviral capsule doses for FIP?

The CURE FIP™ Dual Antiviral Oral Capsules are dosed by body weight, given as one capsule per day for a recommended 12 weeks. The capsules combine GS-441524 with EIDD-1931 in three weight bands.

Body weight	GS-441524	EIDD-1931
Under 2.5 kg	25 mg	5 mg
2.5 to 5 kg	35 mg	8 mg
Over 5 kg	50 mg	12 mg

The reasoning behind the dual approach is explored in our piece on how dual antiviral therapy is changing FIP care, and the relapse-focused findings are detailed in the 78.3% remission study results.

Because EIDD-1931 is teratogenic, it must not be used in pregnant or lactating queens. Always confirm the right band and route with your veterinarian before starting.

How should you start FIP treatment in the UK?

To start FIP treatment in the UK, confirm the diagnosis and form of FIP with your veterinarian, choose the matching antiviral route, and commit to the full 84-day course with monitoring. Skipping steps or stopping early are the most common ways progress is lost.

1. Get a veterinary diagnosis that identifies the form of FIP (wet, dry, ocular, or neurological).

2. Decide with your vet whether injectable GS-441524 or the dual antiviral oral route suits your cat.

3. Confirm the weight-matched dose from the catalog figures above.

4. Follow the daily schedule for the full 12 weeks (84 days) without gaps.

5. Schedule regular bloodwork so your vet can track recovery.

We are clear about what the data shows and what it does not. GS-441524 has strong published evidence behind it, but outcomes vary by cat, and every decision belongs with your veterinarian.

FAQ: Feline Infectious Peritonitis (FIP) Treatment in the UK

Is Feline Infectious Peritonitis (FIP) treatable in 2026?

Yes. Feline Infectious Peritonitis (FIP) is treatable with antiviral therapy built around GS-441524, which has a 92% success rate reported by UC Davis (Pedersen, 2019) and has supported more than 100,000+ cats treated since 2019.

How long does FIP treatment take?

A standard FIP course runs 84 days (12 weeks) under veterinary supervision. The injectable schedule is one subcutaneous injection per day, seven days a week, and the dual antiviral capsules are given once daily for a recommended 12 weeks.

What is the difference between GS-441524 injections and dual antiviral capsules for FIP?

Injectable GS-441524 is dosed per kilogram across all four forms of FIP and reports a 92% success rate (UC Davis, Pedersen 2019). The dual antiviral capsules combine GS-441524 with EIDD-1931, are positioned for wet and dry FIP, and reported 78.3% remission in relapsed cats (Li and Cheah 2025).

Can dual antiviral capsules be used for ocular or neurological FIP?

Some regions note the oral dual route is not recommended once ocular or neurological signs are present, or if the cat cannot eat or defecate. In those cases, discuss the injectable GS-441524 route with your veterinarian.

Where can UK caregivers learn more about FIP survival and monitoring?

UK caregivers can review practical guidance in our FIP survival tips article and always coordinate monitoring, including bloodwork, with their own veterinarian throughout the 84-day protocol.

If your cat has just been diagnosed, you do not have to navigate the choice alone. Explore the antiviral options and speak with our team by visiting the CureFIP treatment options for UK cat owners, and bring what you learn to your own veterinarian so you can build the right plan together.