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Best Feline Infectious Peritonitis (FIP) Oral Treatment

Updated: Jan 18

What is Feline Infectious Peritonitis (FIP)?

Feline infectious peritonitis (FIP) is a viral disease caused by feline coronavirus. It is a rare but fatal disease if left untreated.

What Cause of FIP Infection

Feline infectious peritonitis occurs when feline coronavirus undergoes a mutation during replication. By scientific estimates, this mutation occurs in 2~5% of cats that have contracted the feline coronavirus. It is important to note that while a majority of cats will contract feline coronavirus at some point in their lives, very few cats ever contract FIP.

The 2 Forms of FIP Infection

There are two clinical forms of feline infectious peritonitis (FIP): effusive FIP, also known as wet FIP, and non-effusive FIP, also known as dry FIP. Wet FIP is characterized by the swelling of the abdomen, which is caused by the accumulation of fluid in the cat's body due to internal organ inflammation resulting from FIPV infection and the body's immune response. Dry FIP, on the other hand, is difficult to diagnose as there are no clear clinical symptoms that can be easily observed. A series of tests are required to diagnose a cat with dry FIP.

Veterinarians use several tests to reach a conclusive FIP diagnosis. The tests may include:

  • FCOV/FIP quick test

  • Complete blood examination

  • Tissue samples examination

  • Rivalta test

Feline Infectious Peritonitis Symptoms

Common FIP symptoms include:

  • Persistent fever

  • Lack of desire for food

  • Lethargy

  • Difficulty breathing

  • Poor body coordination

  • Fluid in the abdomen

  • Fluid in the chest

  • Fluid in the lungs

  • Paralysis

  • Ocular symptoms

If your cat displays symptoms of FIP infection, it is crucial not to disregard them, as they may indicate a severe health issue. Unfortunately, many cats suffer from this veterinary disease because their owners are unaware of the gravity of these symptoms and veterinarians may misinterpret them as less serious infections.

2 Treatment Options for Feline Infectious Peritonitis

GS-441524 is the only clinically proven drug for feline infectious peritonitis (FIP), and it is a nucleoside analog similar to the human antiviral Remdesivir. Gilead Sciences, the patent holder of GS-441524, did not pursue its commercialization for animal use, but the black market suppliers in China have stepped in to meet the global demand from desperate cat owners. The two available treatment options for FIP are subcutaneous injections and oral capsules/pills, both containing GS-441524 as the active pharmaceutical ingredient.

Subcutaneous injections are the more reliable and consistent form of treatment for FIP. They are recommended for the first 30 days of treatment or until the cat's symptoms subside and condition stabilizes. Injections are particularly recommended if your cat is not eating or drinking, exhibiting neurological symptoms such as paralysis, has cloudy eyes, poor movement coordination or difficulty breathing, an infected or weak digestive system, or a weak immune system. The injection form of GS-441524 is equally effective in treating both wet and dry FIP.

While injections are considered more reliable than the oral form of GS-441524 in treating FIP, many cat owners prefer the oral option due to the potential discomfort associated with injections. Some cats experience pain or develop an aversion to injections after weeks of treatment, and some may resist the procedure altogether. Additionally, injection site sores may occur due to the acidity of the injected drug. In these cases, oral capsules or pills may be used as an alternative to injections. Concerns about drug resistance to oral administration have been disproven, and the oral form of GS-441524 is equally effective in treating both wet and dry FIP.

Capsules vs Pills

Although oral capsules and pills are equally effective, administering capsules is generally easier than pills. Capsules can be coated with wet cat snacks, making it more likely for cats to swallow them whole, or they can be inserted directly into the cat's mouth due to their smooth texture and lack of taste. Capsules are more expensive and slower to manufacture compared to pills, so manufacturers typically prefer producing pills. However, is the only brand currently offering GS-441524 in capsule form.

Pills in contrast are faster and cheaper to manufacture. They are the first oral FIP treatment product to appear on the market. There are multiple brands that offer pills for treating FIP. Mutian and Aura/Spark, Capella, Lucky, Brava, and Kitty Care are current brands that offer oral pills for the treatment of feline infectious peritonitis. FIP oral pills are uncoated. They are small in size and can be administered without much struggle in a majority of cases. However, in a small number of cases, due to their taste and texture, some cats produce a gaging response and may spit out the pills if it has not travelled far enough down the esophagus, forcing the caregiver to repeat the process. Worse yet, some cats may vomit out the pills shortly after ingestion, thus an unpleasant experience and financial waste for cat owners.

When to switch from injections to oral fip treatment?

We recommend starting every FIP treatment with 30 days of injections. It is the most effective and reliable method of treating FIPV. You should continue the injection for as long as possible, or until such times that

  • your cat can no longer tolerate daily injections.

  • you cat's eating and drinking habits have returned to normal.

  • Your cat no longer exhibit sever FIP symptoms such as neurological and ocular symptoms.

  • Your cat does not experience digestive complications often associated with FIP infections.

  • You can't do not vomit or diarrhoea frequently.

Introduce oral once when all of the above conditions are met. should the condition of your cat noticeably regress, depending on the severity, you may either increase oral treatment dosage and return to injections for the remaining days.

Cost Comparison between Injection and oral GS-441524

The cost of GS treatment, whether in injection or oral pill form, has significantly reduced since their initial introduction. Currently, the prices for both treatment options are comparable to each other.

How Effective are Oral FIP Treatments?

When given at the correct time and dosage, oral FIP treatment can be equally effective as subcutaneous injections in treating feline infectious peritonitis. However, experts in FIP treatment generally agree that cats treated orally are at a higher risk of relapse than those treated with injections during the entire course of FIP treatment. Oral capsules and pills have been found to be less effective in treating cats with neurological forms of FIP or those with frequent vomiting or diarrhea. There are currently no known side effects associated with either injection or oral FIP treatment.


Thanks to the scientific discoveries made by research teams in the USA and manufacturers in China, FIP treatment options are becoming more diverse and accessible. Although injections are still considered the more reliable method of treating FIP, oral capsules and pills can be equally effective when used appropriately and under the correct conditions to treat FIPV. The success of the treatment often depends on the experience and expertise of the veterinarian. If your vet is not experienced in treating feline infectious peritonitis, you may contact us for advice and guidance at

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