Feline Infectious Peritonitis Treatment UK: 2026 Guide

Key takeaway: Feline Infectious Peritonitis ("FIP") is treatable in the UK with GS-441524, the antiviral at the core of modern FIP treatment. The standard course is one subcutaneous injection a day for 12 weeks (84 days), with the daily dose set by which of the four forms your cat has (wet, dry, ocular, or neurological). Across the wider network, 140,000+ cats have been treated since 2019, and the published evidence for GS-441524 is strong.

If your cat has just been diagnosed, this guide walks you through what Feline Infectious Peritonitis (FIP) is, the four forms, how treatment works, what the data shows, and what it costs. Every figure we quote names its source, and every dosing decision belongs with your veterinarian.

A cat resting comfortably at home.

What is Feline Infectious Peritonitis (FIP) and what causes it in cats?

Feline Infectious Peritonitis ("FIP") is a serious viral disease caused by a mutated form of the common feline coronavirus (FCoV). Many cats carry FCoV harmlessly in the gut, but in a small number the virus mutates and triggers FIP.

FIP was once considered almost always fatal. That is no longer the reality. GS-441524 based antiviral treatment has changed the outlook completely, and today most cats diagnosed early and treated properly have a real chance of recovery.

The disease is not a single illness. FIP takes four distinct forms, and each one shapes the treatment plan, so getting the diagnosis right with your veterinarian matters a great deal.

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

Feline Infectious Peritonitis ("FIP") takes four forms: wet (effusive), dry (non-effusive), ocular, and neurological. Ocular and neurological are separate forms in their own right, not sub-types of dry FIP, and each carries its own signs and its own daily dose.

Wet (Effusive) Feline Infectious Peritonitis (FIP)

Wet, or effusive, Feline Infectious Peritonitis ("FIP") is marked by fluid building up in the abdomen or chest. You may notice a swollen, rounded belly, laboured breathing, lethargy, and weight loss despite the fuller tummy.

This is often the fastest-moving form, so prompt diagnosis and early treatment make a real difference.

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

Dry, or non-effusive, Feline Infectious Peritonitis ("FIP") develops without significant fluid build-up. Signs can be vaguer and slower to appear: persistent fever, poor appetite, weight loss, and a generally unwell cat.

Because the signs are subtle, dry FIP can take longer to pin down, which is why ongoing veterinary assessment is so important.

Ocular Feline Infectious Peritonitis (FIP)

Ocular Feline Infectious Peritonitis ("FIP") affects the eyes. Watch for a change in iris colour, cloudiness, inflammation inside the eye (uveitis), and vision loss from lesions in the eye.

Eye colour change is an ocular sign. Ocular FIP needs a higher daily dose than wet or dry disease, so accurate classification by your veterinarian directly shapes the plan.

Neurological Feline Infectious Peritonitis (FIP)

Neurological Feline Infectious Peritonitis ("FIP") affects the brain and nervous system. Signs include seizures, head tilt, loss of balance, paralysis, and disorientation.

Like ocular FIP, the neurological form calls for a higher daily dose because the medicine needs to reach well-protected tissues.

What is the treatment for Feline Infectious Peritonitis (FIP) in the UK?

The treatment for Feline Infectious Peritonitis ("FIP") in the UK is GS-441524, an antiviral given as a daily subcutaneous injection. The standard course is one injection per day, 7 days a week, for 12 weeks (84 days), with the daily dose set by which of the four forms your cat has.

Here is how the daily dose maps to each form, mirroring the four forms above:

FIP form	Daily GS-441524 dose	Schedule	Course
Wet (effusive)	6 mg/kg	1 subcutaneous injection per day, 7 days/week	12 weeks (84 days)
Dry (non-effusive)	8 mg/kg	1 subcutaneous injection per day, 7 days/week	12 weeks (84 days)
Ocular	10 mg/kg	1 subcutaneous injection per day, 7 days/week	12 weeks (84 days)
Neurological	10 mg/kg	1 subcutaneous injection per day, 7 days/week	12 weeks (84 days)

These 6, 8, and 10 mg/kg figures are consistent with current clinical practice. Gokalsing et al. 2025 report the best outcomes within the 5 to 10 mg/kg range once daily, adjusted for FIP type and for neurological or ocular signs. Ansari Mood et al. 2025 similarly describe starting doses adjusted upward by form. Your veterinarian confirms the exact dose for your cat's weight and form.

Which GS-441524 injectable strength is right?

The injectable comes in three strengths so the volume per dose fits your cat. Pick the strength and size with your veterinarian based on your cat's weight and form.

Product	Strength	Sizes	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

Every course follows the protocol for your cat's product, under veterinary supervision.

Is there an oral option for Feline Infectious Peritonitis (FIP)?

Yes. For many cats, an oral option can follow the injection phase. The CURE FIP™ Dual Antiviral Oral Capsules (€179.00) combine GS-441524 + EIDD-1931 and are commonly used after 2 to 4 weeks of GS-441524 injections, including in ocular and neurological cases, or once the cat is stable.

The key advantage of the dual capsule is simple dosing: one capsule a day for your cat's weight class, with no mg calculation and no counting capsules.

Weight class	Daily dose
0 to 2.5 kg (0 to 5.5 lb)	1 capsule per day
2.5 to 5 kg (5.5 to 11 lb)	1 capsule per day
over 5 kg (over 11 lb)	1 capsule per day

The recommended oral course is 12 weeks. Because the dual capsule contains EIDD-1931, it is not for pregnant, nursing, or breeding cats, nor for cats that are vomiting, have diarrhoea, cannot eat or defecate normally, or are under 1 year old with wet (effusive) FIP. There is also the EIDD-1931 Oral Capsules (€69.00) option, dosed by your veterinarian. Decisions between injectable and oral routes should always be made with your veterinarian.

How does GS-441524 treatment work for Feline Infectious Peritonitis (FIP)?

GS-441524 works by blocking the virus behind Feline Infectious Peritonitis ("FIP") from replicating, which gives the cat's body the chance to recover. As the viral load falls, many cats start eating, moving, and playing again, often within the first weeks of treatment.

The evidence base is genuinely strong, and we are clear about what each study shows. In Pedersen et al. 2019 (J Feline Med Surg 21(4):271-281), injectable GS-441524 monotherapy delivered a 92% success rate, meaning 24 of the 26 cats that completed treatment remained healthy. In other words, more than 9 out of 10 cats that completed injectable GS-441524 treatment stayed healthy.

Later work reinforces this picture. Ansari Mood et al. 2025 (Sci Rep 16:1037) reported 94.12% survival in a cohort of 629 cats treated with GS-441524. The systematic review by Gokalsing et al. 2025 (Pathogens 14(7):717) found 84.6% overall success across 11 studies and 650 cats, which means more than 8 out of 10 cats were treated successfully.

For the dual antiviral approach, our own data from about 46 treated cats show 78.3% remission on GS-441524 + EIDD-1931, roughly 8 out of 10 cats reaching remission. These are statistics, not promises: every cat is different, and there are no guarantees in medicine. The one guarantee we do offer is that you can cancel any time before your order ships for a full refund.

If you are still weighing up your options, our broader guide to what UK owners should know about an FIP cure puts the evidence in plain terms.

What does Feline Infectious Peritonitis (FIP) treatment cost in the UK?

The cost of Feline Infectious Peritonitis ("FIP") treatment depends on your cat's weight, the form of FIP, and the product and strength your veterinarian chooses, because dose scales with body weight over the 12-week (84-day) course. A larger cat on a higher dose uses more medicine than a small cat on a lower dose.

For reference, the GS-441524 injectables are listed at €79.00 (20 mg/ml), €89.00 (30 mg/ml), and €119.00 (40 mg/ml), the CURE FIP™ Dual Antiviral Oral Capsules at €179.00, and the EIDD-1931 Oral Capsules at €69.00. For a full worked breakdown for the UK, see our dedicated FIP treatment cost guide for the UK.

What should you avoid during Feline Infectious Peritonitis (FIP) treatment?

During Feline Infectious Peritonitis ("FIP") treatment, some common products can work against your cat and should be avoided unless your veterinarian advises otherwise. Keeping the treatment environment clean of these makes the antiviral course more straightforward.

• Fluoroquinolone antibiotics

• Spot-on flea medications

• Lysine supplements

• Immune boosters

If a secondary bacterial infection appears, your veterinarian may add an antibiotic specifically for that. Veterinary supervision is part of treatment from start to finish, including the step down from injections to oral capsules and the monitoring that confirms remission.

FAQ

Is Feline Infectious Peritonitis (FIP) treatable in the UK in 2026?

Yes. Feline Infectious Peritonitis ("FIP") is treatable in the UK with GS-441524 based antiviral therapy, given under veterinary supervision. The published evidence is strong, and across the wider network 140,000+ cats have been treated since 2019.

How long is the treatment course for Feline Infectious Peritonitis (FIP)?

The standard GS-441524 injectable course for Feline Infectious Peritonitis ("FIP") is 12 weeks, which is 84 days, with one subcutaneous injection per day, 7 days a week. The recommended dual-capsule oral course is also 12 weeks. Your veterinarian confirms the length based on your cat's response.

What is the success rate of GS-441524 for Feline Infectious Peritonitis (FIP)?

For injectable GS-441524 monotherapy, Pedersen et al. 2019 reported a 92% success rate, with 24 of the 26 cats that completed treatment staying healthy. The systematic review by Gokalsing et al. 2025 found 84.6% overall success across 11 studies and 650 cats. These are statistics rather than guarantees, and every cat responds differently.

Can I give Feline Infectious Peritonitis (FIP) treatment as a capsule instead of an injection?

Often yes. For Feline Infectious Peritonitis ("FIP"), the CURE FIP™ Dual Antiviral Oral Capsules are commonly used after 2 to 4 weeks of GS-441524 injections, including in ocular and neurological cases, or once the cat is stable. Dosing is one capsule a day for your cat's weight class, and the choice between routes is made with your veterinarian.

Which form of Feline Infectious Peritonitis (FIP) needs the highest dose?

Ocular and neurological Feline Infectious Peritonitis ("FIP") both call for the highest daily dose, 10 mg/kg, compared with 6 mg/kg for wet FIP and 8 mg/kg for dry FIP. This reflects the need to reach the eyes and nervous system, and your veterinarian sets the exact dose for your cat.

If your cat has just been diagnosed, you do not have to face it alone. Learn more about the GS-441524 treatment options and speak with the CureFIP Europe team or your own veterinarian about the plan that fits your cat. With early diagnosis and the right protocol, many cats go back to eating, playing, and curling up at home.