Treating feline infectious peritonitis (FIP) with the antiviral GS-441524 typically costs between $150 and $1,150 for the medication alone over a standard 12-week course, based on a small 6.6-pound cat with uncomplicated disease. The total cost varies widely depending on which pharmacy you use, what form of the drug you choose, how much your cat weighs, and whether the disease involves the eyes or brain.
Medication Cost by Pharmacy
GS-441524 is now available as a compounded medication through several US pharmacies, and pricing differs substantially between them. For a 3 kg (6.6 lb) cat with wet or dry FIP and no eye or neurological involvement, a Best Friends Animal Society comparison found the following 12-week treatment costs:
- Wedgewood (oral suspension): $148.50
- Specialty Vet Pharmacy (oral suspension): $186.73
- Wood Dale (oral suspension): $732
- Ethos (oral suspension): $746.55
- Mixlab (tablets): $755.16
- Avrio: $756
- Las Colinas (capsules): $840
- Stokes (tablets): $1,146.60
These estimates don’t account for weight gain during treatment, which is common as your cat recovers and means you’ll need increasing amounts of medication over the 12 weeks. The actual total will be somewhat higher than these baseline figures. Oral suspensions tend to be cheaper than tablets or capsules, though some cat owners find tablets easier to administer.
Why Your Cat’s Weight Matters
GS-441524 is dosed by body weight, so a 12-pound cat costs roughly twice as much to treat as a 6-pound cat. The standard starting dose for uncomplicated wet or dry FIP is 4 to 6 mg per kilogram of body weight, given daily for 12 weeks. Younger cats and those with wet FIP (the form that causes fluid buildup) tend to start at the lower end of that range, while dry FIP cases start higher.
If your cat has eye involvement without neurological signs, the starting dose doubles to 8 mg/kg daily. Neurological FIP requires 10 mg/kg daily. These higher doses can push medication costs to two or even three times the estimates above, since you’re using significantly more drug each day for the same 12-week period.
Treatment Duration: 12 Weeks or Less
The standard treatment course is 84 days (12 weeks) of daily oral medication. After treatment ends, cats are typically monitored for several months to watch for relapse. A 2024 study published in the journal Viruses found that a shorter 42-day course at a higher dose (15 mg/kg) produced equal results to the standard 84-day regimen in cats with the wet form of FIP, with all cats remaining in complete remission at 168 days after starting treatment. This shorter protocol could potentially cut medication costs in half for eligible cats, though your veterinarian would need to determine if it’s appropriate for your cat’s specific situation.
Veterinary Visits and Bloodwork
The medication itself is only part of the bill. Your cat will need regular veterinary checkups and blood tests throughout treatment to track progress and watch for side effects. A complete blood count runs around $35, and a chemistry panel costs $35 to $45 per session at a diagnostic lab, though your vet clinic may charge more with exam fees included.
Most veterinarians recommend bloodwork at the start of treatment, at several checkpoints during the 12 weeks, and again after treatment ends. Budget for at least three to five rounds of lab work, plus the associated office visits. Depending on your area and clinic, each visit with bloodwork might run $100 to $250, adding $300 to $1,000 or more to the total over the course of treatment and follow-up monitoring.
Supportive Care Costs
Cats with FIP often need additional medications beyond the antiviral, especially early in treatment when they may be underweight, dehydrated, or not eating well. Common supportive treatments include appetite stimulants, anti-nausea medication, B12 supplementation, and liver support supplements. Individually these are relatively inexpensive, typically $10 to $40 each, but they add up when combined over several weeks. Cats with the wet form may also need fluid drainage procedures at the start of treatment, which can cost $200 to $500 per visit depending on sedation requirements.
Realistic Total Budget
For an average-sized cat with uncomplicated wet or dry FIP, you can expect to spend roughly $500 to $2,500 total when combining medication, bloodwork, vet visits, and supportive care. A small cat treated with one of the lower-cost pharmacy options could come in under $500 for medication alone. A larger cat with neurological FIP treated at a higher-priced pharmacy could see medication costs alone exceed $3,000 before vet fees.
The wide range reflects real differences in pharmacy pricing, cat size, disease severity, and how smoothly treatment goes. Cats that respond quickly and gain weight steadily tend to cost less overall than those needing dose adjustments, extended treatment, or emergency visits for complications. Asking your veterinarian to get quotes from multiple compounding pharmacies before starting treatment is one of the most effective ways to manage the cost, since the price difference between the cheapest and most expensive options can be nearly tenfold for the same drug.