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CaliciX for Cats: What It Is and How It Works
CaliciX is the FCV-positioned name for our EIDD-1931 oral capsules, used under veterinary supervision to help manage feline calicivirus (FCV), a common oral and upper respiratory infection in cats. It works with the antiviral EIDD-1931 and is dosed by body weight every 12 hours. CaliciX is a separate product from our FIP antivirals and from HerpX, our feline herpesvirus option, so matching the right product to the right virus matters.
A cat resting comfortably at home.
What Is CaliciX for Cats?
CaliciX is the feline calicivirus (FCV) version of our EIDD-1931 oral capsules, an antiviral given by mouth to support cats fighting FCV-related oral and respiratory disease. The active ingredient is EIDD-1931, the same molecule used in oral FIP protocols, but here it is positioned specifically for FCV.
The CaliciX line is offered in the catalog as EIDD-1931 Oral Capsules (FIP and FCV treatment), priced at AED149.00, with 60 capsules per bottle. Your veterinarian will confirm whether CaliciX, or the stronger CaliciX Max option in the same line, best fits your cat.
It is worth being clear about our range. GS-441524 remains the hero antiviral at the center of our FIP work, while CaliciX is our EIDD-1931 answer for feline calicivirus. Two different viruses, two different tools.
What Is Feline Calicivirus (FCV) and How Is It Different from FIP?
Feline calicivirus (FCV) is a highly contagious virus that causes mouth ulcers, oral pain, drooling, and upper respiratory signs such as sneezing and nasal discharge. It is different from Feline Infectious Peritonitis (FIP), which is caused by a mutated feline coronavirus and is treated with GS-441524 based antivirals.
FCV is one of the main causes of oral and respiratory disease in cats, and it is a frequent driver of chronic mouth inflammation. If you are unsure which virus your cat has, our guide on the difference between feline calicivirus and feline herpesvirus can help you and your veterinarian sort the signs.
Because FCV, feline herpesvirus, and FIP each need a different product, an accurate diagnosis from your veterinarian is the essential first step before any antiviral is chosen.
How Does CaliciX Work Against Feline Calicivirus?
CaliciX works through its active ingredient EIDD-1931, an antiviral that interferes with viral replication so the cat's immune system can gain ground against the infection. It is given orally, by body weight, on a fixed twice-daily schedule set by your veterinarian.
Antivirals like EIDD-1931 target the virus itself. This is different from antibiotics, which do not act on FCV and are used only when a separate bacterial infection is present.
CaliciX is intended to be paired with supportive care: pain control, hydration, nutrition support, and dental or oral care as your veterinarian directs. Antiviral treatment and good nursing care work best together.
What Are the Signs of Feline Calicivirus in Cats?
The most recognizable signs of feline calicivirus (FCV) are painful mouth ulcers, drooling, reluctance to eat, and inflammation of the gums and mouth. Many cats also show sneezing, nasal discharge, and eye irritation.
Common signs to watch for include:
Mouth and tongue ulcers
Drooling and pawing at the mouth
Refusing food or eating much less
Red, inflamed, or bleeding gums
Sneezing and nasal discharge
Lethargy and fever during a flare
A cat that suddenly stops eating is a common and urgent presentation. Our article on feline calicivirus mouth ulcers and why a cat will not eat explains this pattern in more detail.
Some cats develop long-term, severe oral inflammation known as feline chronic gingivostomatitis. If your cat has persistent mouth disease, read our overview of feline chronic gingivostomatitis and FCV and discuss it with your veterinarian.
How Is CaliciX Different from HerpX and GS-441524?
CaliciX, HerpX, and our GS-441524 products treat three different viruses and are not interchangeable. CaliciX (EIDD-1931) is for feline calicivirus, HerpX (famciclovir) is for feline herpesvirus, and GS-441524 based products are for FIP.
Product | Target virus | Active ingredient |
CaliciX / CaliciX Max | Feline calicivirus (FCV) | EIDD-1931 |
HerpX | Feline herpesvirus (FHV-1) | Famciclovir |
GS-441524 Antiviral Injectables | FIP | GS-441524 |
CURE FIP™ Dual Antiviral Oral Capsules | FIP | GS-441524 + EIDD-1931 |
Matching the product to the virus is the whole point. Because FCV and feline herpesvirus can look similar, our detailed comparison on how to tell FHV-1 and feline calicivirus apart is a useful reference before you choose a treatment path with your veterinarian.
How Is CaliciX Dosed for Cats?
CaliciX uses the EIDD-1931 Oral Capsules dosing of 1 capsule (15 mg) per 2.5 kg of body weight, given every 12 hours, with a standard course of 60 days. Each bottle contains 60 capsules, and the dose is set by your cat's weight, so weigh accurately and confirm the schedule with your veterinarian.
A simple way to think about the course is:
Confirm the FCV diagnosis with your veterinarian.
Weigh your cat so the by-weight dose is correct.
Give the capsule every 12 hours as directed, without skipping doses.
Continue the standard 60-day course unless your veterinarian advises otherwise.
Return for recheck so treatment can be adjusted to your cat's response.
CaliciX is not intended for ocular or neurological cases, and it is not suitable for a cat that is not eating or not defecating. In those situations your veterinarian will decide on a different plan.
One important safety note: EIDD-1931 is teratogenic, which means it must not be used in pregnant or lactating queens. Always confirm your cat's status with your veterinarian before starting.
Who Is CaliciX For, and Who Should Not Use It?
CaliciX is for cats diagnosed by a veterinarian with feline calicivirus (FCV), particularly those with oral and upper respiratory signs who are still able to eat and defecate. It is an oral antiviral option positioned specifically for FCV in the Gulf.
CaliciX may suit a cat that:
Has a veterinary diagnosis of FCV
Shows mouth ulcers, oral pain, or upper respiratory signs
Is still eating and defecating
Can take an oral capsule on a twice-daily schedule
CaliciX is not appropriate for a cat that:
Is pregnant or lactating (EIDD-1931 is teratogenic)
Has ocular or neurological disease
Is not eating or not defecating
Has not been assessed by a veterinarian
For a fuller picture of what FCV looks like and how it is managed in our climate, see our feline calicivirus symptoms and care guide for the Gulf.
How Much Does CaliciX Cost in the Gulf?
The EIDD-1931 Oral Capsules behind the CaliciX line are listed at AED149.00 per bottle of 60 capsules. Because dosing is by body weight and the standard course runs 60 days, the number of bottles your cat needs depends on weight and your veterinarian's plan.
We believe in being transparent about product and cost up front. The best way to estimate a full course is to share your cat's weight with our team or your veterinarian, who can map the by-weight dose to the right quantity.
Our focus on clarity and outcomes is the same one that has supported more than 100,000 cats since 2019 across our antiviral programs. That experience shapes how we explain protocols, dosing, and what the evidence does and does not show.
Does CaliciX Treat FIP or Feline Herpesvirus?
No. CaliciX is positioned for feline calicivirus (FCV) only, and it should not be used as an FIP or feline herpesvirus treatment. FIP is treated with GS-441524 based antivirals, and feline herpesvirus is managed with HerpX, our famciclovir option.
The active ingredient in CaliciX, EIDD-1931, does also appear in our CURE FIP™ Dual Antiviral Oral Capsules alongside GS-441524, where the dual antiviral approach reported 78.3% remission (Li and Cheah 2025). For monotherapy, GS-441524 injectables reported a 92% success rate at UC Davis (Pedersen, 2019). Those figures apply to FIP, not to FCV, and should never be read as CaliciX results.
FAQ
Is CaliciX the same as GS-441524?
No. CaliciX is an EIDD-1931 oral capsule positioned for feline calicivirus (FCV), while GS-441524 is the hero antiviral used in our FIP products. They target different viruses and are not interchangeable.
Can CaliciX be given to a pregnant cat?
No. The active ingredient EIDD-1931 is teratogenic, so CaliciX must not be used in pregnant or lactating queens. Confirm your cat's status with your veterinarian before starting any antiviral.
How long is a CaliciX course?
The EIDD-1931 Oral Capsules behind CaliciX have a standard 60-day course, dosed at 1 capsule (15 mg) per 2.5 kg of body weight every 12 hours. Your veterinarian may adjust based on your cat's response.
Can CaliciX be used if my cat has stopped eating?
CaliciX is not suitable for a cat that is not eating or not defecating, or for ocular or neurological cases. A cat that has stopped eating needs prompt veterinary assessment and supportive care first.
Does CaliciX cure feline calicivirus?
Feline calicivirus (FCV) care focuses on managing infection and helping your cat recover from flares, not on making guarantees. CaliciX is used under veterinary supervision as part of a plan that includes supportive care, and your veterinarian will guide expectations for your individual cat.
If your cat has been diagnosed with feline calicivirus, the next step is a clear conversation about the right plan. You can explore the available treatment options and speak with our team or your own veterinarian through our CureFIP Gulf clinic, so decisions stay evidence-led and comfortable for you and your cat.
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