What Is the Best Treatment for FIP in Cats?

The best-supported treatment for Feline Infectious Peritonitis ("FIP") in cats is GS-441524 antiviral therapy given over a full 84-day protocol under veterinary supervision. GS-441524 monotherapy reported a 92% success rate at UC Davis (Pedersen, 2019), and CureFIP has supported 100,000+ cats treated since 2019. The right dose depends on which of the four forms of FIP your cat has: wet, dry, ocular, and neurological.

A cat resting comfortably at home.

What is the best treatment for FIP in cats?

The best treatment for FIP in cats is a complete 84-day course of GS-441524, an antiviral that targets the feline coronavirus behind FIP. Evidence shows a 92% success rate with GS-441524 monotherapy in the UC Davis field study (Pedersen, 2019), which is why it sits at the core of modern FIP treatment.

FIP was once considered untreatable. Today, with GS-441524 started early and dosed correctly for the form of FIP, many cats reach remission and go on to live full lives.

The key word is complete. FIP treatment is not a quick fix. It is a structured 12-week (84-day) protocol that runs every single day, followed by an observation period, all guided by your veterinarian.

What is GS-441524 and why is it the core of FIP treatment?

GS-441524 is a nucleoside analog antiviral that blocks the feline coronavirus from replicating, which is the mechanism at the heart of effective FIP treatment. It is the hero ingredient of CureFIP and the most studied molecule in FIP care today.

The landmark data comes from UC Davis, where Pedersen and colleagues reported a 92% success rate using GS-441524 (Pedersen, 2019, PMC6435921). That figure applies specifically to GS-441524 monotherapy delivered by injection.

If you want a deeper look at the numbers behind the molecule, our guide on how effective GS-441524 treatment is for FIP walks through the study detail. We are clear about what the data shows and what it does not.

How is FIP treated based on its form?

FIP treatment is tailored to which of the four forms your cat has, because each form calls for a different daily dose of GS-441524. FIP takes four forms, wet, dry, ocular, and neurological, and each shapes the treatment plan and the milligrams per kilogram your veterinarian prescribes.

The dosing below reflects the GS-441524 Antiviral Injectables and is delivered as 1 subcutaneous injection per day, 7 days a week, for 12 weeks (84 days), per Pedersen et al., UC Davis (PMC6435921). Confirm the exact dose and volume with your veterinarian.

Form of FIP	GS-441524 injectable dose	Schedule	Duration
Wet / Effusive	6 mg/kg	1 injection daily	84 days
Dry / Non-effusive	8 mg/kg	1 injection daily	84 days
Ocular	10 mg/kg	1 injection daily	84 days
Neurological	10 mg/kg	1 injection daily	84 days

Wet / Effusive FIP

Wet FIP is the effusive form, marked by fluid buildup in the abdomen or chest that can cause a swollen belly or labored breathing. It often progresses quickly, so early diagnosis and treatment matter.

For wet FIP, the GS-441524 injectable dose is 6 mg/kg once daily for 84 days. Because breathing can be affected, your veterinarian may monitor your cat closely in the first days of treatment.

Dry / Non-effusive FIP

Dry FIP is the non-effusive form and produces little or no fluid, which can make it harder to spot. Signs include weight loss, fever that does not respond to antibiotics, lethargy, and inflammatory masses in organs.

For dry FIP, the GS-441524 injectable dose is 8 mg/kg once daily for 84 days. If you are still in the diagnosis stage, our article on what to do if your U.S. vet suspects FIP explains the next steps.

Ocular FIP

Ocular FIP involves the eyes, causing color changes in the iris, cloudiness, inflammation, or vision problems. It signals that the virus has reached tissues behind the blood-eye barrier, which requires a higher dose.

For ocular FIP, the GS-441524 injectable dose is 10 mg/kg once daily for 84 days. This higher dose helps the antiviral reach the eye at effective levels.

Neurological FIP

Neurological FIP affects the brain and spinal cord and can cause wobbliness, seizures, behavior changes, or partial paralysis. It requires the highest dose because the antiviral must cross the blood-brain barrier.

For neurological FIP, the GS-441524 injectable dose is 10 mg/kg once daily for 84 days. Neurological cases benefit from especially close veterinary follow-up.

Injectable or oral GS-441524: which route is best for FIP?

Injectable GS-441524 carries the strongest published efficacy data and is the reference standard, while oral options add flexibility for cats and families who struggle with daily injections. The best route depends on the form of FIP, your cat's temperament, and your veterinarian's guidance.

Injectable GS-441524 monotherapy is tied to the 92% success rate from UC Davis (Pedersen, 2019). The oral dual antiviral approach, which combines GS-441524 with EIDD-1931, reported 78.3% remission in previously relapsed cats (Li and Cheah, 2025). These are two different products for two different situations, so the figures should never be blended.

Route	Product	Positioned for	Key figure
Injectable	GS-441524 Antiviral Injectables	All four forms, per dose table	92% success (UC Davis, Pedersen 2019)
Oral dual	Cure FIP™ Oral Capsules	Wet/dry FIP	78.3% remission in relapsed cats (Li and Cheah 2025)

The Cure FIP™ Oral Capsules are dosed by body weight: under 5.5 lb takes GS-441524 25 mg + EIDD-1931 5 mg; 5.5 to 11 lb takes GS-441524 35 mg + EIDD-1931 8 mg; over 11 lb takes GS-441524 50 mg + EIDD-1931 12 mg. The schedule is 1 capsule per day for a recommended 12 weeks.

The oral dual route is positioned for wet and dry FIP. Some regions note it is not recommended once ocular or neurological signs are present, or if the cat cannot eat or defecate. To understand how the two molecules work together, see our explainer on dual antiviral capsules and the full breakdown for American cat owners.

How long does FIP treatment take?

FIP treatment takes 84 days, a standard 12-week protocol of daily GS-441524 given under veterinary supervision. Skipping days or stopping early raises the risk of relapse, so consistency across the full 84 days is essential.

After the 84-day course, most protocols include an observation period of about 12 weeks. During this window your veterinarian watches for any return of signs before declaring sustained remission.

Regular blood work is part of the journey. Our guide to reading your cat's blood work during FIP treatment explains which numbers your veterinarian tracks and why they matter.

How much does FIP treatment cost?

FIP treatment cost depends on the product, strength, and your cat's weight, since the dose scales with body weight over the full 84 days. CureFIP lists injectable and oral options at fixed USD prices, shown below exactly as cataloged.

Product	Strength	Price (USD)
GS-441524 Antiviral Injectables, 8ml	15 mg/ml	$49.00
GS-441524 Antiviral Injectables	20 mg/ml	$69.00
GS-441524 Antiviral Injectables	30 mg/ml	$89.00
GS-441524 Antiviral Injectables	40 mg/ml	$119.00
GS-441524 Antiviral with Vitamin B12	20 mg/ml + B12 50mcg/ml	$75.00
GS-441524 Antiviral with Vitamin B12	30 mg/ml + B12 50mcg/ml	$95.00
Cure FIP™ Oral Capsules	dosed by weight	$129.00

Heavier cats and higher-dose forms such as ocular and neurological FIP use more medication, which affects the total. Your veterinarian can help you estimate the quantity your cat needs across the 84-day protocol.

What makes a treatment provider trustworthy?

A trustworthy FIP treatment provider is transparent about protocol length, dosing structure, cost, and the exact studies behind each claim. Look for clear product-matched evidence rather than vague promises.

• Clear 84-day protocol and dosing by FIP form

• Efficacy figures attributed to named studies

• Honest pricing with no hidden conversions

• A record of scale, such as 100,000+ cats treated since 2019

• Insistence on veterinary supervision throughout

For a broader overview of the landscape, our FIP treatment in the USA FAQ guide answers the questions American caregivers ask most.

FAQ

What is the best treatment for FIP in cats?

The best treatment for FIP in cats is a complete 84-day course of GS-441524, which reported a 92% success rate as monotherapy at UC Davis (Pedersen, 2019). The exact dose depends on whether your cat has wet, dry, ocular, or neurological FIP, so work with your veterinarian.

Can FIP be treated at home?

Much of the daily GS-441524 protocol can be given at home, but diagnosis, dosing, and monitoring must be directed by your veterinarian. Regular check-ins and blood work help confirm your cat is responding across the full 84 days.

Is injectable or oral GS-441524 better for FIP?

Injectable GS-441524 monotherapy carries the 92% success figure from UC Davis (Pedersen, 2019), while the oral Cure FIP™ Oral Capsules pair GS-441524 with EIDD-1931 and reported 78.3% remission in relapsed cats (Li and Cheah, 2025). The best route depends on the form of FIP and your veterinarian's advice; the oral dual route is positioned for wet and dry FIP.

How long before I see improvement in my cat?

Many caregivers notice appetite and energy improving within the first days to weeks of GS-441524 treatment, but the full protocol still runs 84 days. Early signs are encouraging, yet stopping early raises relapse risk, so complete the course under veterinary guidance.

How many cats have been treated with GS-441524?

CureFIP has supported 100,000+ cats treated since 2019, reflecting the growing real-world experience with GS-441524 based FIP treatment. This scale sits alongside published evidence rather than replacing it.

If your cat has just been diagnosed, you do not have to navigate this alone. Explore the available options and talk with our team or your own veterinarian by visiting CureFIP USA, where every protocol is built around your cat and guided by your veterinarian.