Feline infectious peritonitis (FIP) used to be a death sentence. It’s caused by a mutated form of feline coronavirus, a very common and usually harmless virus, and it mostly affects young cats, especially those under two, often from shelters, rescues or multi-cat homes.
Since mid-2024, US vets have been able to prescribe a legal, compounded form of GS-441524, the antiviral that turned FIP into a treatable disease. The question most owners face now isn’t whether treatment exists, but what it will cost. The answer depends on three things: your cat’s weight, the form of FIP, and which pharmacy fills the prescription.
What the Medication Costs
GS-441524 is dosed by weight, so the price is easiest to work out from the total amount your cat needs. Two published US prices at the time of writing (November 2026):
| Product | Listed price | Per 50 mg |
|---|---|---|
| Stokes Pharmacy (Bova) 50 mg tablets, 40-count | $546 | About $13.65 per tablet |
| Stokes Pharmacy (Bova), 10- or 20-count | $195 / $325 | $19.50 / $16.25 |
| Compounded 50 mg/mL oral suspension, 120 mL bottle, at a large online pet pharmacy | $480 | About $4 per mL |
Stokes lists the same prices for its 50 mg/mL suspension as for its tablets, and adds shipping (about $9.50 standard). Prices from compounding pharmacies differ a lot, and they change, so it’s worth asking your vet which pharmacies they can prescribe through and comparing.
A standard 84-day course at 15 mg/kg a day
| Cat’s weight | GS-441524 needed | At $13.65 per 50 mg | At $4 per 50 mg |
|---|---|---|---|
| 2 kg (4.4 lb) | About 2,520 mg | About $690 | About $200 |
| 3 kg (6.6 lb) | About 3,780 mg | About $1,030 | About $300 |
| 4 kg (8.8 lb) | About 5,040 mg | About $1,380 | About $400 |
| 5 kg (11 lb) | About 6,300 mg | About $1,720 | About $500 |
These are drug costs only, at the exact dose. In practice the bill runs higher: tablets are given in quarter-tablet steps, so doses get rounded up; kittens gain weight during treatment and need their dose raised; and products sold in fixed bottle sizes mean you pay for whole bottles. The suspension is dated for 90 days from manufacture, so a course may be filled in more than one order.
Why the Form of FIP Changes the Price
The current treatment guidance from the Bova group (Taylor, Tasker, Gunn-Moore and colleagues, updated May 2024) recommends oral doses of:
- 15 mg/kg once a day (or split into two doses) for wet (effusive) and dry FIP without eye or nerve involvement,
- 15–20 mg/kg a day when the eyes are affected,
- 10 mg/kg twice a day when there are neurological signs, because the drug has to cross into the brain.
A 4 kg cat with neurological FIP therefore needs about 6,720 mg over 84 days — roughly $540 to $1,840 in medication at the two prices above, compared with about $400 to $1,380 for the same cat with wet FIP.
The Rest of the Bill
The medication is only part of the cost.
| Part of treatment | What it involves | Typical cost |
|---|---|---|
| Diagnosis | Exam, bloodwork, and usually analysis of any fluid; PCR testing and ultrasound are often added | About $160–$490 for a basic workup; can pass $1,500 with imaging or a specialist |
| Rechecks | Weight, exam, bloodwork at about 2, 6 and 12 weeks, and again about 4 weeks after stopping | About $130–$400 each, for an exam plus bloodwork |
| Hospital care at the start | IV fluids, fluid drainage, or injectable antivirals for very sick cats | Varies widely; ask for an estimate |
There’s no single definitive test for FIP. Vets build the diagnosis from the cat’s age and history, blood results, imaging and — most usefully — the fluid itself when there is any, according to the AAFP/EveryCat FIP diagnosis guidelines. Fluid analysis is more informative than blood tests, which is one reason the workup cost varies so much between cats.
A typical total — diagnosis, a full course of oral GS-441524 and four rechecks — comes to roughly $1,000–$4,800 for an average-sized cat, before any hospital stay.
The 42-Day Option
The biggest saving is a shorter course, for the right cat. In a randomized controlled study of 40 cats with wet FIP (Zuzzi-Krebitz et al., 2024, Viruses), cats given oral GS-441524 at 15 mg/kg for 42 days did as well as cats treated for 84 days: 19 of 20 cats in each group survived, and all survivors were in complete remission by day 168.
The Bova guidance now says the 42-day course can be considered for cats that respond quickly and have normal blood results — and, where available, a normal acute-phase protein (AGP) test — at weeks 4 and 6. It notes the reduced cost as one reason to consider it. It isn’t right for every cat: the study included only wet FIP without neurological or eye signs.
What to Expect From Treatment
Results are good for a disease that was almost always fatal:
- In a study of 307 cats treated with legally sourced compounded remdesivir and GS-441524 (2020–2022), 84.4% were alive at the last follow-up after treatment, and 10.8% relapsed — 15 during treatment and 18 after it.
- Cats that achieved a complete response within 30 days were more likely to be alive at the end of treatment.
The Bova guidance expects improved energy and a normal temperature within about 48 hours. Cats are weighed weekly so the dose keeps up with weight gain.
Relapse usually means restarting at a higher dose — typically 5–10 mg/kg a day more — and a repeat 12-week course, which means paying for a second round of medication. Keeping up the rechecks, including the one about four weeks after stopping, is the best way to catch it early.
About Unregulated Sources
Before compounded GS-441524 became available, many US owners bought it from unregulated suppliers. Cornell’s Feline Health Center describes those sources as often unreliable. A legal compounded product needs a prescription, so it also means your vet is involved in dosing and monitoring, which is where relapses and dose problems are caught.
Ways to Keep the Cost Down
- Compare pharmacies. The same dose can cost several times as much from one compounding pharmacy as another.
- Ask about the 42-day course if your cat has wet FIP without eye or neurological signs and responds quickly.
- Weigh accurately so the dose matches your cat, not a guess.
- Ask about remdesivir versus oral GS-441524. The Bova guidance notes that oral GS-441524 is cheaper than remdesivir for the cat’s weight; injections are mainly used for cats too sick to take oral medication at first.
- Ask which tests matter at each recheck. The guidance suggests bloodwork “as cost allows” at some visits.
A Note on Insurance
Accident-and-illness policies may cover FIP diagnosis and treatment if signs didn’t appear before coverage began. Because compounded medications are involved, check whether your policy covers compounded drugs, and whether a waiting period applies — our Pet Insurance Waiting Period Tracker can help with the dates.
Frequently Asked Questions
How much does FIP treatment cost? For most cats, the GS-441524 itself costs roughly $200–$1,700 for a standard 84-day course at published US pharmacy prices, depending mainly on the cat’s weight and the pharmacy. With the diagnostic workup and three or four rechecks, a typical total is about $1,000–$4,800. Cats that need hospital care at the start, cats with neurological or eye involvement, and cats that relapse cost more.
Is GS-441524 legal in the US? Yes, as a compounded medication prescribed by a veterinarian. Stokes Pharmacy began offering compounded oral GS-441524 with the Bova Group on June 1, 2024, and other compounding pharmacies, including Wedgewood, have since added it. It is not an FDA-approved drug, and a veterinary prescription is required.
How long is FIP treatment? The standard course is 84 days (12 weeks) of daily medication. A randomized study of 40 cats with wet FIP found a 42-day course at 15 mg/kg worked as well as 84 days, and some vets now use the shorter course for cats that respond quickly and have normal blood results at weeks 4 and 6. That roughly halves the drug cost.
What is the success rate of FIP treatment? High for a disease that was almost always fatal before antivirals. In a study of 307 cats treated with legally sourced compounded remdesivir and GS-441524 between 2020 and 2022, 84.4% were alive at the last follow-up after treatment ended, and 10.8% relapsed. In a smaller randomized study of oral GS-441524, 38 of 40 cats survived and were in complete remission.
Why does FIP medication cost more for some cats? Because it’s dosed by weight and by the form of the disease. The usual oral dose is about 15 mg/kg a day, while cats with eye involvement may need 15–20 mg/kg and cats with neurological signs about 20 mg/kg a day split into two doses. Kittens gaining weight during treatment also need their dose raised, so a heavier cat or one with neurological FIP needs more medication.
What happens if FIP comes back after treatment? Relapse can happen during treatment or after it, and relapses after treatment mostly appear within about 60 days of stopping. The usual approach is to restart at a higher dose, typically 5–10 mg/kg a day more than before, and a repeat 12-week course has been used successfully. That means paying for a second course, so it’s worth keeping up the scheduled rechecks.
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