Frequently Asked Questions

Basic Questions

Feline infectious peritonitis (FIP) is a fatal infectious disease of cats. There are two basic forms - wet (effusion) and dry (non-fusion). FIP can also affect the eyes and central nervous system. In this case, we are talking about the ocular or neurological form of FIP. You can find more info practically on this whole portal, as it is entirely dedicated to FIP and its treatment.

No. The coronavirus is highly contagious and most cats will be exposed to it at some point during their life. FCoV is shed through feces, so cats who share a litter box or groom one another are exposed to the benign form of the virus. Cats who have a healthy immune system will pass the coronavirus with little to no issue other than a bout of diarrhea and/or cold-like symptoms.

Cats who have a weakened or not fully developed immune system may not be able to pass the coronavirus, and the virus mutates into FIP. Once mutated into FIP, the virus is no longer contagious.

There is believed to be a genetic component with FIP, so biological litter mates may share the same genetic predisposition that allows FCoV to mutate. A family history of FIP does unfortunately increase the likelihood that siblings will develop FIP.

There is no unambiguous test that definitely confirms the diagnosis of FIP. Diagnosis is usually the result of a combination of clinical signs, blood tests, titer results, the presence of fluid in the abdominal or thoracic cavity, and other specific tests. Check page of FIP diagnostics .

GS-441524 (abbreviated GS) is an experimental antiviral drug (nucleoside analog) used during field trial led by Dr. Niels Pedersen at UC Davis in 2017.

The drug exists in injectable and oral form under the names of various brands.

The treatment lasts 84 days. Of course, tablets have the slight disadvantage of dosing accuracy, as it is very difficult to break the tablet into smaller parts than into quarters, so the real price will be slightly higher. You never have to buy medication for the whole treatment at once. Dosage in relapse, other types of FIP, etc. may increase, which then corresponds to a higher price.

Approximate price of treatment according to the type of FIP and the form of the drug in CZK (EUR) per kg / 84 days
GSWet FIPDry FIPOcular FIPNeurological FIPRelapse
Injections (CZK / kg)5,9428411.810
Injections (€ / kg)242840.481
Tablets (CZK / kg)8416.377
Tablets (€ / kg)840.667

Recommended duration of treatment based on the original clinical study of Dr. Pedersen lasts for at least 12 weeks of subcutaneous injections.

After twelve weeks, blood testing is recommended and the clinical status of the cat should be assessed to determine whether treatment should be continued.

General Questions

The tablets can be taken with a small amount of food, or half an hour after a meal. Make sure you have a sufficient drinking regimen. Due to the absorption limit in the GI tract, it is appropriate to divide the dose into twice daily, especially at high doses (eg neurological FIP). At the same time, a more even level of the active substance in the blood is achieved.

Please pay attention to weighing cats in the treatment of FIP. In particular, do not use cheap personal scales designed for weighing adults. These scales have great inaccuracy. I know that a lot of people weigh a cat by weighing themselves with and without a cat, and the difference is the weight of the cat. Alternatively, you weigh the cat directly, but the personal scales are not designed for such a low weight. So this weight may be far from the truth. However, the fact that the personal weight has an stated accuracy of 0.1 kg does not in fact mean that it is also the highest weighing error. In fact, deviations of 0.5 kg or more usually occur with personal weight. All you have to do is stand on the scale differently, put it in another place, or weigh yourself repeatedly, etc etc ...

It should be noted that a deviation of 0.5 kg in a person weighing 50 kg means 1%, but in a cat that weighs e.g. 2.5 kg already means a deviation of 20%. But it is the knowledge of the cat's weight that is crucial in determining the correct dose of the drug.

Therefore, for weighing cats, I recommend either kitchen scales or even better baby scales, which also have a fairly large area, and for a restless cat you will use the function of blocking the weight data so that you can read it at rest.

Especially young or very emaciated cats, which are expected to increase significantly during treatment, weigh regularly at least 1-2 times a week.

If you don't want to buy a weight for treatment, just go to the vet once a week and take the cat there. Many veterinarians even have a weight freely available in the waiting room.

And a little more advice. In any treatment, a slight overdose is better than an underdose. Therefore, if in doubt about the accuracy of the weighing, it is better to round up or use the highest weight from repeated weighing.

Example of a suitable weight: Baby Ono

FIP can be successfully treated with both forms of the drug. Injections are slightly cheaper, but are especially useful if the cat does not want to receive anything at all at the beginning of treatment, or vomits if it has diarrhea, which could have a significant effect on the absorption of the active substance. Unfortunately, for most cats, injections are also very painful.

The tablets are convenient, but also slightly more expensive, in addition, they can usually be divided into a maximum of 1/4, so it is not possible to achieve a completely accurate dosage, as with injections.

Yeah. It is possible, if the cat's health allows it. It is important to note that gabapentin is a prescription drug.

L-lysine should NEVER be given to a cat with FCoV or FIP infection because it is antagonistic to arginine, which is essential for immune function. In addition, it is possible that lysine affects the effect of GS-441524.

Dabbing some isopropyl rubbing alcohol on the pads of a cat’s paws can help reduce a fever quickly. If kitty is willing to sit still for a bit, you can also wrap an ice pack in a towel and rest it against his or her body. A fan can also help reduce a fever but again, only if the cat is fairly sedentary and stays in the stream of the cool air. Fevers that persist for >24 hours should be addressed by a veterinarian. Severe fevers over 105F require urgent or emergency care.

Under no circumstances give human antipyretics to a cat !!! Most of them are fatally toxic to cats, even in small doses.

Pumpkin puree is very effective for both diarrhea and constipation. The soluble fiber in pumpkin will regulate and deliver the correct amount of water to the GI tract. It’s also packed with vitamins that are beneficial to cats, and most cats will eat pumpkin voluntarily if stirred into their food. There’s no harm in adding some to every meal, as a preventative either. Be sure it is pure pumpkin puree, NOT pie filling.

Another option is a probiotic, such as Fortiflora which promotes proper gut health and enhances the immune system. This is an excellent addition to any cat’s diet, and can be given daily indefinitely.

If the effusion is in the heart cavity or lungs, the effusion should be drained as much as possible.

If the effusion is in the abdomen, the fluid should only be drained if it is interfering with the cat’s breathing and then, only enough fluid should be removed to restore the cat’s breathing to normal.

Although manufacturers claim that medicines can be stored at room temperature, in reality, it is best to store the solution in the refrigerator. In addition, GS441524 needs a very low pH for its stability. Many manufacturers do not realize that the higher the concentration, the lower the pH required for the solution to be stable. Poor pH adjustment may be the reason why some brands may show problematic results in concentration tests. In any case, low storage temperatures contribute to higher stability. Injectable solutions should last for about 1 year in the refrigerator. It is simply good to follow similar principles as other injectable solutions - cold and dark storage.

Ideally, surgical procedures should be postponed or avoided, as they will stress the cat’s immune system. According to Dr Pedersen’s recommendation, the blanket statement is that he suggests waiting until completing 12 weeks of treatment plus the 3 month window of observation.

There are exceptions to this rule depending on the specific situation of the cat being treated. If laboratory results indicate that the cat is in good health, consult your veterinarian about the risks and benefits of sterilization / castration during treatment.

In addition, the behavior of an uncastrated cat can be much more stressful than castration alone. In this case, it is better for the cat to be neutered during treatment, if its health allows it, than during a three-month observation period.

Castration during treatment is so maybeif the good clinical condition of the cat allows it. The ideal time for castration could be the last third of treatment, but at least it remains after castration 1 week until the end of treatment.

There is a reasonable assumption that GS-441524 in the small intestine has an absorption ceiling of about 10 mg / kg. For this reason, especially at higher doses, it is good to divide the total daily dose into 2 times a day.

The success rate of treatment is around 80%. It depends on the type of FIP, its degree, or when treatment started. There are also cases where the treatment did not work at all.

During treatment, it may happen that the cat also suffers from a secondary infection and may need ATB.

Safe ATBs:

  • Penicillin type ATB - Amoxicillin / Clavulanate (Clavaseptin, Clavamox, Noroclav, Xiclav, Synulox)
  • Tetracyclines - Doxycycline (Ronaxan, Doxyhexal),
  • Lincosamides - Clindamycin

Not recommended ATBs:

  • Fluoroquinolones - They cross the blood-brain barrier and may cause secondary neurological symptoms, therefore their use is not recommended: Baytril, Enrofloxacin (Enroxil), Zeniquin, Marbofloxacin (Marbocyl), Pradofloxacin (Veraflox), Orbifloxacin (Orbax).
  • Cephalosporines (Convenia)

dr. Pedersen believes that no supplements are necessary during GS treatment. However, due to the experience with many treated cats, it is advisable to use hepatoprotectors (Liver, Hepapet, Zentonil etc...) and probiotics (e.g. Fortiflora), or to administer B12. But the basis is a good and meat-rich diet because of arginine, which cats cannot synthesize themselves.

It is not recommended.
Do not use Revolution, Stronghold, Frontline or other flea/tongs agents during FIP treatment. The most important factor in treatment is the environment. Vacuum every day (floors, wardrobes, bed linen, everything cats come in contact with) and wash all bed linen. Every day, comb the cat with a comb for fleas. You can prepare a mixture of water and apple cider vinegar (2: 1), which you apply to a cloth, and rub the cat daily. The flea solution repels. Although Revolution or Stronghold are relatively safe options, it is not clear whether there is an interaction between the active substance (selamectin) and GS441524 and whether the treatment process cannot be affected.

Not. It is not recommended. And it is not recommended even during posttreatment.

In some cases, the treatment will take place almost immediately, the cat's temperature will return to normal, he will start to be more active, he will start eating… Most cats will respond to the treatment within 2 days. With wet FIP, most of the fluid should normally be absorbed within 7-14 days. Either way, the therapeutic effect of any form of FIP in terms of improving the clinical condition, if you have the right dosage, you should notice a maximum of about 3-4 days. If this does not happen, it is time to think about changing the medicine or its form (eg from tablets to injections or vice versa) or increasing the dose. However, it is possible that the cat also suffers from another associated health problem that you will have to deal with with a veterinarian. FIP is often accompanied by other diseases and maybe your cat will need ATB, for example.

If the treatment does not work within 4 days, or even the cat's condition worsens, it is possible that it is not FIP at all and you should deal with this situation quickly. The danger of concentrating too much on FIP, even if the treatment does not seem to work, is that you may miss the real illness your cat is suffering from, and as a result may die just because you do not know about it and are not looking for it. If you have a dose of 12 mg / kg or higher, and the cat is not improving or deteriorating, it is almost certain that there is another serious problem than FIP.

Resistance to GS-441524 may also occur rarely, but is very rare during initial treatment and occurs rather in the form of partial resistance to relapse treatment, which can often be overcome by increasing the dose. Complete resistance requires treatment with another active substance, such as molnupiravir.

Injections are administered subcutaneously. Since the cat gets them 84 for the entire treatment period, you will alternate spots. Injections are given 24 hours apart. Ideally, your veterinarian would teach you injections. The injections are quite painful for the cat, so it is possible to get help from a family member.

The only known side effects are painful injection and possible skin lesions at the injection site. It should be noted that the cat receives 84 injections over 84 days.

The dose depends on the weight of the cat. However, the basic dosage is 6 mg GS per 1 kg live weight of a cat in wet and dry uncomplicated FIP. Ours is also available calculator:

Neurological and ocular forms require dosages of up to about 8-12 mg / kg. Be sure to consult a specific dosage.

If you like formulas, then calculating is simple.

i = m * d / c

i: injection dose [ml]
m: cat's weight [kg]
d: dosage of active substance (GS441524) for a given type of FIP [mg / kg]
c: concentration [mg/ml]


Cat's weight is 2kg,
dose for your FIP type is 5mg/kg. 6mg / kg,
concentration of injection solution is 15mg / ml.

Enter into formula and you will get:

i = 2 * 6/15 = 0.8 ml

Neurological FIP means that the FIP has penetrated the blood-brain barrier and there are neurological symptoms of the disease, such as weakness of the hind legs, inability to jump somewhere without hesitation, poor coordination, and seizures may also occur.

Similarly, the ocular form means that the FIP virus has penetrated the blood-ocular barrier and caused inflammation in the eye (uveitis - inflammation of the middle layer of the eye ball), it also manifests visually, see photo. Neurological and ocular forms are often associated.

Answers by Dr. Pedersen

The questions and answers below are compiled from a series of e-mails between Dr. Niels Pedersen and owners of cats who are currently being treated with GS441524 or who have already completed the treatment cycle.

There is no scientific evidence that any available flea treatment has a negative effect on GS-441524 treatment. However, I am personally opposed to the use of systemic insecticides to kill fleas in cats. Their use is based on the fact that the insecticide is less toxic to the cat than to the fleas that feed on it. Using them to control fleas is similar to military tactics, as artillery is called in to help the enemy cross your line.

It would be great to have a simple test that could determine exactly when the cure took place, but in its absence we can only follow a significant and gradual improvement in external health (activity, alertness, appetite, weight gain, coat quality) and all the most important blood test values (hematocrit, white blood cell count, lymphocyte count, total protein, albumin, globulin and A / G ratio). The 12-week treatment period is based on clinical trials with both GC376 and GS-441424 and represents the period that allows for the maximum rate of cure. There is no doubt that some cats will not be cured for more than 12 weeks until they can be cured sooner (ie 8-10 weeks). However, premature termination of treatment will always lead to a reduction in the proportion of cured cats, and the sooner you stop treatment, the higher the rate of relapses. Finally, it is up to the owner and his veterinarian to decide when to stop treatment and to start the post-treatment observation period.

Yes, this is possible as an alternative to not providing treatment. But it may be better, based on the half-life of GS in the blood, to give the full dose every other day instead of half the dose every day. However, like skipping doses when the drug is available and significantly changing the time of day for injection, this is something that should not become a routine practice.

Occasional fluctuations during administration do not matter as the effective blood level is more than 24 hours. There is some flexibility in dosing, but the constant change in administration time depending on the owner's schedule does not say well about the owner's attitude towards treatment and his cat.

Not. Missing a dose is not serious because effective blood levels are maintained for more than 24 hours. However, skipping a dose should definitely not become a rule.

There is no evidence that deworming drugs have a negative effect on GS treatment. Like any other drug in the treatment of FIP, there should be good reasons for its use (ie the benefits outweigh the risks).

Avoid stress and overcrowding. Keep cats in small separate groups. Consider isolating kittens from their mother after weaning to avoid exposure to FCoV. Do not mix very young kittens with older cats. If you can limit exposure to the coronavirus until 12-16 weeks of age, when the immune system is more developed, the likelihood of developing FIP may be reduced. Breeders should avoid mating between cats that have had close relatives that have died of FIP or that have produced kittens that have developed FIP. Also, follow established vaccination protocols and follow proper husbandry practices to limit further infections. Clean and disinfect cages, boxes and bedding regularly. You can easily destroy the coronavirus with bleach and other disinfectants.

If you have lost a cat due to FIP, remove any cat-related items that you cannot wash or disinfect, such as scrapers or soft toys. Clean and disinfect everything else in the environment. Time will take care of the rest, because viruses of this type do not have a long lifespan in the environment. It is recommended for several months (about 2 months or more), which is the standard for most infectious diseases.

A cat with FIP should respond very quickly to treatment and no other medication is needed at this time unless clearly indicated. However, prednisolone, or corticosteroids in general, have rules for their discontinuation. Depending on how long they have been given, they cannot be planted immediately. Be sure to consult your veterinarian for the correct procedure.

Although theoretically possible, we have not yet seen the FIP-cured cats develop the disease later. Therefore, I would focus on curing your FIP positive cat. Do not treat a cat that only secretes enteric coronavirus. This cat has a very low risk of developing FIP and treatment with enteric coronavirus carriers will only promote the occurrence of drug-resistant strains.

Vaccination or castration is not required during treatment. Healing the cat is paramount. There will be plenty of time after treatment to resolve the issue of castration. Personally, I am not a strong supporter of FVRCP vaccines (polyvalent vaccines) or the need to vaccinate cats against rabies (unless required by state or local legislation) or administering FeLV to cats that are at low risk for infection. If we treat a cat with FIP, it should be treated in accordance with standard professional care, locality (rabies) and your practice. In short, treat the cat like any other cat, but have it cured first.

It would probably not be appropriate to alternate these forms on a daily basis. But there is probably no problem with the transition from one form to another.

Yes, at least one company in China also produces the oral form GS-441524, which it claims will work just like injections. This is not surprising, since the modifications required to convert injectable drugs into an oral form are well known. All drugs for HIV / AIDS and hepatitis C were also transformed into an oral form. However, like many others, you may find it more difficult to give tablets to cats than to inject. They usually adapt to the injections over a short period of time, but if they don't agree with the pills, it still gets worse and worse. Therefore, if you go this route, do not invest much in it until you are sure that you will be able to give the tablets to your cat.

It doesn't have to mean anything if urea and creatinine are in the normal range. High phosphorus content may not mean anything yet. I recommend checking the values in a month.

The lymphocyte count is only slightly higher than normal, but in reality it is good. A low lymphocyte count would indicate that the infection is active and severe, while a high number would indicate that it elicits an immune response.

Cats and other small animals are not as consistent in their systemic temperature as humans, and the fluctuations you see are not uncommon. The problem is that the more you worry, the more you measure the temperature and the more of these fluctuations you will see. For this reason, we are not very afraid of these fluctuations. It is much worse when temperatures are consistently higher than 39.5 ° C. It is important to note the overall condition of the cat, its appetite, activity levels and clinical signs. In short, fluctuations like these are fine unless they become permanent and are associated with loss of appetite and activity. If your cat is otherwise well and there is no evidence of a persistent fever, we recommend that the cat be only at home, where it is possible to protect it from unnecessary stress and monitor it closely.

I prefer digital rectal thermometers, which are characterized by high measurement speed. Do you measure temperature during rest and not after a certain time of physical activity? Temperatures may vary. One is higher, one is higher.

We can observe what will happen in the coming days and hope for the best. If a reaction develops at the injection site, it is possible that this is the cause of the symptoms we are seeing. It can result in an open wound, but it can also improve on its own. Although no one wants serious reactions after an injection, it can be said that an injection is still a better choice.