FIP Treatment

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Before starting treatment

FIP treatment lasts for at least 84 days. Pay special attention to cats with a wet form of FIP and fluid in the pleural (chest) cavity. If fluid builds up there, the cat may have trouble breathing and the heart is very stressed. It may be necessary to drain some of the fluid before starting treatment. Firstly, because the increase in the volume of fluid in the chest cavity can be so rapid that the cat may not live to see the effect of the treatment, and secondly, because the injection itself can be such a shock to the cat that its heart may not be able to withstand it.

Choose form of medicine



  • Price. Most of the injectables are significantly less than the oral form
  • Precision in dosing. You can adjust the daily dose to the exact weight of the cat, whereas the oral form is dosed based on weight range.
  • Medicine is not dependent on the digestive system and is fully absorbed into their blood stream, so they are guaranteed to be getting the maximum benefit of the GS.
  • The field study was completed using injectable, so there is professionally curated data available.


  • Injections sting and some cats do not tolerate the pain well.
  • Injection site sores are likely going to happen, regardless of how carefully the shots are administered. In most cases, the sores will heal on their own with little to no need for intervention.


  • Ease of administering. Many cats will take the capsules/tablets willingly if coated with a treat or given in a pill pocket.
  • The oral forms are readily available at all times.


  • Price. The oral form is considerably more expensive than injectable.
  • The dose is not accurate. It adjusts in steps, depending on how you are ablet to split the tablet. The dose remains constant within a specific weight range.
  • If the cat has gastrointestinal problems, absorption of the drugs is questionable at best. The cat may vomit the tablets or there may be a problem with absorption in the gut.
  • Lack of data. There are no field studies for the oral form, so no confirmed data.

Determination of the correct dose

The dose depends on the form of the FIP and the weight of the cat. Dosage for a given form of FIP can be found in calculator. During treatment, the cat is needed continuously to weigh (at least once a week) and adjust the dose accordingly. It is good to get used to recording the course of treatment in any form of treatment protocol, where you will record the weight, temperature, dose of the medicine and notes about the clinical condition of the cat.

If the weight of the cat is temporarily reduced, the dose is not reduced. Short-term weight loss may be due to loss of effusion fluid.

There may be a worsening of the condition, or an outbreak of neurological or ocular FIP, and you will be forced to increase the dose. However, in case of deterioration during treatment, it is always good to visit a veterinarian, because FIP is very often accompanied by secondary infections and these are treated with antibiotics.

Please do not confuse dosing in mg/kg and ml/kg!!! The dosage in mg/kg is independent of the drug concentration and expresses the amount of active substance per 1 kg body weight of the cat. The dosage in ml/kg, on the other hand, is specific for the solution for injection solution and depends on its concentration. It expresses the volume of solution you apply per 1 kg of live weight. Dosage conversion in mg/kg vs. ml/kg according to the concentration of the solution for injection can be found in the following table.

15 mg/ml15
16 mg/ml16
16.5 mg/ml16.5
16.7 mg/ml16.7
16.9 mg/ml16.9
17 mg/ml17
18 mg/ml18
20 mg/ml20
21 mg/ml21

It should be noted that the above dosages are for guidance only. Determining the correct dosage is extremely important, especially at the beginning of treatment, when it is necessary to reverse the course of the disease. In cats older than 3 years, we recommend choosing a dose of 7 mg/kg for wet and dry FIP without neurological and/or ocular symptoms. It also depends on whether it is a classic treatment or a treatment of relapse. In case of relapse, a dose at least 2-5 mg/kg higher than in the previous round of treatment is recommended.

GS-441524 application interval

Medicines, whether in injectable or tableted form, are given every 24 hours. Choose a time that you will be able to adhere to throughout the treatment. For some tablets, or even for small kittens, it is sometimes better to divide the application into two daily doses.

Supportive treatment

Hepatopretics (eg Liver, Hepapet) and probiotics (eg Fortiflora) should also be given to cats during treatment, and B12 in case of severe anemia.

Cats with FCoV or FIP should never be given lysineas it is antagonistic to arginine, which is essential for immune function. In addition, it is possible that lysine affects the effect of GS-441524.

How to find out if the treatment works

In some cases, the improvement is nocieable almost immediately, the cat's temperature will return to normal, it will become more active, it will start eating… With wet FIP, the liquid should be absorbed, usually within 7-14 days. Either way, improvement should be visible within about 4 days. If this does not happen, it is time to think about changing the drug, increasing the dose, or consider other potential health issue.

Treatment by injections

Injections are administered subcutaneously every 24 hours.

Given the duration of treatment, you will need to rotate the injection sites to prevent any skin lesions. The injections are quite painful, so it is possible that you will not be able to administer them without the help of another person. If you have no experience with injections, it is a good idea to arrange with a veterinarian to teach you. Due to the viscosity of the injection solution, I recommend green needles 0,8x16mm or 0,8x25mm. If the cat behaves aggressively during administration, it is good, for example, to wrap it in a blanket and leave accessible only the places where you want to inject. There are even "burritos" for cats that can immobilize it but also allow you to inject.

Most cats are angry immediately after application to the point that they are best calmed by food. Often, even when the injection becomes a daily ritual, it may happen that when you give the cat a bowl of food, you can inject it during feeding so that the cat almost does not notice.

Injection site sores are cleared of surrounding hair and gently cleaned 4 or more times a day with sterile cotton balls soaked in 1:5 dilution of household hydrogen peroxide. They usually do not require any more sophisticated treatment and heal within 2 weeks or so.

General how-to for injection administration can be found here.

Spots for injection application

Video on how to administer injection (Dr. Pedersen):

Other videos can be found this page.

What to look out for when injecting

The GS solution is very acidic. As a precaution against lesions or necrosis of the skin at the injection site, it is important to always inject with a clean needle and at least wipe the site with water moistened with gauze / cloth (neutralize) after application. Be careful not to get too much injection site and keep track of how much GS may have leaked.

If GS leaks a lot, it is advisable to consider repeating the application to maintain the dosage. If GS leaks from the injection site, it may be due to the volume of solution being applied, the needle being not inserted deep enough, or the needle diameter being too large. If possible, apply the GS solution slowly and slowly pull the needle out of the injection site.

After injection, slight bleeding may occur due to damage to the subcutaneous tissue. If it is just a few drops, it is a relatively common and unproblematic condition that does not require urgent veterinary care. If the bleeding is heavy or the cat behaves unusually painfully after GS application (especially for an atypical manifestation of pain that lasts for more than a few minutes after application), it moves uncoordinated, has difficulty breathing or is paralyzed, it is time to seek urgent veterinary care!

When calculating the GS dose, it is recommended to round to the nearest higher tenth.

Treatment with pills

The tablets are usually administered without any problems. The tablets should be administered on an empty stomach and you should make sure that the cat drinks enough. However, there are situations when you need to give your tablets with food for some reason. It doesn't matter either. If cat vomits within 2 hours after the tablet administration, you may need to give administer the tablet again.

Regular check-ups by a veterinarian

In order to possibly adjust the dose during treatment and to avoid prolongation, or to minimize the risk of possible relapse after treatment, it is a good idea to have a haematological and biochemical blood test during treatment, ideally at weeks 4 and 8. Treatment that is developing in the right direction has been shown to return gamma globulins to a reference range by the end of treatment.

End of treatment

Just before the end of the treatment (84) days, it is good to have the blood examined and according to the results, taking into account the clinical condition of the cat, to decide on its termination or extension. In addition to the classic hematological and biochemical examination, it is good to have plasma protein electrophoresis performed, which will provide much more accurate results. This is followed by a 3-month period, the so-called PostTreatment. When this period has passed without relapse, the cat can be declared cured.

At the end of treatment, the following values should be normal:

  • albumin
  • globulins
  • A/G ratio > 0,65
  • bilirubin
  • lymphocytes
  • neutrophiles
  • hematocrit, hemoglobin, erythrocytes
  • gamaglobulins (from electrophoresis)

Post-Treatment Period

Afte treatment completion, there is an observation period of 12 weeks. During this period, it is good to give the cat peace of mind and protect it from stressful situations. It is recommended that control blood samples be taken at least at weeks 6 and 12. At the end of the observation period, the cat can be considered cured.

If you are still missing information, check out FAQ. Very nice summary of FIP treatment from Dr. Pedersen can be found here.