Miscellaneous Questions and Answers regarding FIP 2020

Updated December 2020


1. I have been told that if the kitty misses 1-day dosage the next dosage has to be doubled to cover the previous dosage?

No. Missing one dosage is not serious, because effective blood levels are sustained over 24 h. However, missing a dose is something that should be avoided if all possible as it can become a habit.


2. Must the GS Dosage be administered exactly 24 hours day to day? What if work gets in the way and I am late for the next dosage by 3 to 4 hours or in another scenario what if my vet is closing early dur to unforeseen reasons can I give the jab earlier? If I do what will the best time be for the next jab for the following day.

No, for the same reason given in question #1. There is flexibility in dosing, but again, continually varying the time of administration to meet owner’s schedules does not speak well for the commitment of the owner to the treatment and their cat.


3. I have heard that using flea prevention medication such as advocate, revolution, frontline can affect GS effectiveness. If Yes, can kitties use Seresto collar even if its active ingrediencies is absorbed into the fatty layer of the skin.

There is no scientific evidence that any available flea treatment has a negative effect on GS-441524 treatment. However, I am personally against the use of systemic insecticides to control fleas on a cat. They work on the fact that the insecticide is less toxic for the cat than for the fleas that feed on it. Their sole use for flea control is an admission of defeat that is akin to the military tactic of calling in the artillery on your position when it is being overrun by the enemy.


4. I was told that if your GS medication is running out, and you are still waiting for shipment of the new vail. You can reduce the dosage by half for that day rather than having use all and skipping a day or two

Yes, this can be done as the best alternative to giving no treatment. It may be better, based on the half-life to GS in the bloodstream, to give a full dose every other day rather than a half dose every day. However, like skipping doses when drug is available and greatly altering the daily injection time, it is something that should not become a routine practice.


5. Is completing 12 weeks (83 days) recommended or is it a must? I’ve been told that if kitty A/G ratio goes back to 0.7 even if you are only 3 to 4 weeks in you can actually stop and monitor if there is a relapse

It would be a great discovery to have a simple test that could accurately determine when a cure has occurred, but in its absence, we can only go by significant and progressive improvement in signs of outward health (activity, alertness, appetite, weight gain, quality of coat) and all of the most relevant 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 field trials with both GC376 and GS-441424 and is a period that allows for the maximum proportion of cures. There is no doubt that some cats are not cured even over 12 weeks and some evidence that some can be cured sooner (i.e, 8- 10 weeks). However, early cessation of treatment will always lead to a decrease in the proportion of cats that are cured, and the sooner you stop a treatment, the higher the relapse rate. In the end, it is up to the owner and their veterinarian to make the decision when to stop treatment and began the post-treatment observation period.


6. Is there any harm to keep giving GS even if the A/G ratio has gone back to normal before the 12 weeks are completed

No, there is no harm in treating longer than usual, but treatment is expensive and hard on both cat and owner. That is why I have given definite instructions on when and how to extend treatment.


7. I’ve been told that its best to increase the dosage from 8mg to 10mg if the bloodwork shows no improvement on the A/G ratio for the first 4 weeks

It is common to divide a treatment into 4-week blocks, ending with new blood tests. The rule is not to increase the dosage unless it is strongly indicated by outward response to treatment (see question #5) and blood test results. If there is good reason to increase the dosage, it should be for at least +2 to +5 mg/kg daily and for a minimum of 4 weeks. Of course, dramatic changes in the form of FIP, e.g. ocular or neurological, require immediate changes in dosage.


8. I’ve heard that deworming medication cannot be used during GS treatment period

There is no evidence that any deworming medications have a negative effect on GS treatment. Like any extra medication added to the mix, there should be strong reasons to use it (i.e., benefits outweigh risks).

-Niels C. Pedersen, DVM, PhD, School of Veterinary Medicine, UC Davis.


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