Treatment Options for FIP in Cats: GS-441524 vs. EIDD-1931 – Which One Is Best?
- CUREFIP.COM
- Mar 3
- 7 min read
Updated: Jul 24
Feline Infectious Peritonitis (FIP) is one of the most serious diseases affecting cats worldwide, with a 96% mortality rate. For years, it was considered untreatable. But in recent times, antiviral medications have changed the outlook.
Two compounds—GS-441524 and EIDD-1931—are now being used to treat FIP. Both have drawn attention for their ability to stop the virus, but they come from different backgrounds and follow different paths in terms of availability and use.
CureFIP offers two main treatment options:
GS-441524 – the leading choice in FIP treatment, with a 92% recovery rate.
EIDD-1931 (MolnuFIP™) – a newer, more affordable antiviral that is 7.3x more potent than GS-441524.
This article compares their benefits, drawbacks, and dosages to help you choose the best solution for your beloved cat.
What is GS-441524?
GS-441524 is a nucleoside analog that inhibits the replication of the coronavirus responsible for FIP. With a 92% recovery rate, this drug has saved thousands of cats worldwide and remains the preferred choice for many veterinarians.
GS-441524 has been used to treat cats with FIP since 2019. It was originally developed during the research that led to Remdesivir, a human antiviral. Over the years, GS-441524 has become the primary treatment choice for FIP in many countries. It is widely recognised in veterinary communities and supported by real-world data from thousands of treated cases.
The compound works by blocking the virus’s ability to make copies of itself. With daily dosing over roughly 12 weeks, the treatment aims to give the cat’s immune system a chance to recover while suppressing the virus.
One of the advantages of GS-441524 is the growing amount of treatment data available. Dosing protocols are well-established and can be tailored to different types of FIP—whether it’s the wet form with abdominal fluid, the dry form affecting organs, or the neurological and ocular types.
While availability depends on region and local regulations, GS-441524 is already in wide use across Europe. It is typically offered in oral form, allowing owners to give the medication at home with guidance from veterinary professionals or FIP treatment support networks.
Benefits of GS-441524:
Effective against all types of FIP (wet, dry, neurological, and ocular).
Safe for long-term use – 0% cytotoxicity (does not harm cells).
Available in injection and capsule form, offering flexible dosing options.
Provides treatment for up to 84 days without a high risk of mutagenicity.
Drawbacks of GS-441524:
Higher cost makes it inaccessible for some pet owners.
FIP virus may develop resistance, especially in neurological cases.
Daily injections can be challenging, especially for long-term treatment.
GS-441524 Dosage:
Wet FIP: 6 mg/kg every 24 hours
Dry FIP: 8 mg/kg every 24 hours
Neurological/Ocular FIP: 10 mg/kg every 24 hours
Treatment Duration: 12 weeks (84 days)
What Is EIDD-1931 (MolnuFIP™)?
EIDD-1931 is the active metabolite of Molnupiravir, specifically developed for FIP. Clinical studies have shown that EIDD-1931 is 7.3 times more potent than GS-441524, with a 97% success rate.
Unlike GS-441524, which halts viral replication directly, EIDD-1931 works by introducing small changes into the virus’s genetic material. These changes make it harder for the virus to survive and continue spreading inside the cat’s body.
The oral form of EIDD-1931 has made it a convenient option for owners who prefer at-home administration. It is usually compounded specifically for veterinary use, with protocols evolving as more experience is gathered from treatment groups and veterinarians.
While formal clinical data on EIDD-1931 in cats is still limited compared to GS-441524, interest is growing. Some owners and vets see it as an alternative path when GS-441524 is not available, or when a different antiviral approach is desired.
Benefits of EIDD-1931 (MolnuFIP™):
More affordable – 1/10th the cost of GS-441524.
More potent – requires a lower dose for the same effect.
Capsule form – no need for injections, making administration easier.
No reported drug resistance so far.
Recovery typically begins within one week, with a reported 97% success rate.
Drawbacks of EIDD-1931 (MolnuFIP™):
2.8% cytotoxicity – mild effects on the liver and kidneys with prolonged use.
Short half-life – must be given every 12 hours to maintain effectiveness.
Not recommended for neurological or ocular FIP, due to limited penetration into the central nervous system.
Maximum treatment duration is 60 days – if FIP persists, switching to GS-441524 is necessary.
EIDD-1931 (MolnuFIP™) Dosage:
Wet/Dry FIP: 2.3 mg/kg every 12 hours
Ocular FIP: 3.5 mg/kg every 12 hours
Neurological FIP: Not recommended
Treatment Duration: Maximum 60 days
Why Must It Be Given Every 12 Hours?
The half-life of EIDD-1931 is only 1-1.3 hours, much shorter than GS-441524 (~4 hours). This means the drug must be administered more frequently to remain effective.
Practical Comparison: GS-441524 vs EIDD-1931
Availability and Access
GS-441524 has become more widely available over the past few years, especially through trusted suppliers working closely with veterinary professionals and FIP treatment networks. In many European countries, it is not yet formally approved as a veterinary drug but is used under compassionate-use or off-label frameworks. This accessibility, along with growing familiarity among vets, makes GS-441524 a practical choice for many.
EIDD-1931, on the other hand, is newer to the veterinary field. While it is available in some regions and through certain channels, its access is more limited and less standardised. Owners often rely on specialised suppliers or compounding pharmacies that are willing to formulate the product for feline use.
Treatment Duration and Ease of Use
GS-441524 is usually given daily over 12 weeks. Its oral version has made it easier for owners to administer at home, although injectable versions are still used in some cases, particularly at the beginning of treatment or in more advanced cases. The routine is structured and widely documented, making it easier to follow with veterinary support.
EIDD-1931 is also administered daily, and like GS-441524, it is available in oral form. Protocols for EIDD-1931 are still developing, but many are modelled after existing GS-441524 regimens. The convenience of oral dosing appeals to owners looking for at-home care options. However, the lack of standardised protocols may require closer communication with suppliers or vets.
Clinical Confidence and Experience
GS-441524 benefits from several years of accumulated case data, both from veterinary professionals and from owners who have gone through treatment. Its track record includes successful outcomes in thousands of cats globally, including those with neurological and ocular forms of FIP.
EIDD-1931 has a growing number of treatment cases, but fewer formal records and published outcomes specific to cats. That said, the compound’s success in human antiviral therapy adds a layer of scientific credibility to its potential. As more field cases are tracked and shared, confidence in its use may increase.
Which One Should You Choose?
For many owners, the decision comes down to access, available guidance, and the specific needs of their cat. Both GS-441524 and EIDD-1931 offer antiviral action and can lead to recovery. However, GS-441524 currently has the advantage of broader adoption, more treatment data, and greater familiarity among vets and support communities.
That does not mean EIDD-1931 lacks value. As research continues and usage expands, it may become a strong complementary or alternative option—particularly in regions or cases where GS-441524 is not suitable or accessible.
Choose GS-441524 if:
You want a well-established treatment with the highest safety level.
You can afford a higher cost.
Your cat has neurological or ocular FIP, as EIDD-1931 is not recommended for these cases.
You want to avoid long-term cytotoxicity risks.
If your cat has kidney and liver issues.
If your cat has a poor appetite, is vomiting, or has diarrhoea.
Choose EIDD-1931 (MolnuFIP™) if:
You need a more affordable solution without sacrificing effectiveness.
Your cat has wet or dry FIP, but not neurological or ocular FIP.
You can administer the medication every 12 hours consistently.
Recommended Treatment Combinations:
Neurological/Ocular FIP:
Start with GS-441524 injections for 30 days, then switch to GS-441524 capsules for the remaining 84 days.
Wet/Dry FIP without complications:
Start with EIDD-1931 for 30 days. If there are no liver and kidney problems, then assess the condition. If symptoms persist, continue EIDD-1931 up to 60 days. If FIP is still present, switch to GS-441524.
Conclusion: FIP Can Now Be Treated!
FIP is no longer a hopeless diagnosis. With effective antiviral options like GS-441524 and the emerging use of EIDD-1931, cat owners now have reason to be optimistic. Both treatments have their place in the evolving world of FIP care.
Both GS-441524 and EIDD-1931 (MolnuFIP™) offer effective solutions for treating FIP.
GS-441524 is ideal for those looking for the safest and most complete treatment, especially for neurological and ocular FIP.
EIDD-1931 (MolnuFIP™) provides a more affordable alternative with high effectiveness for wet and dry FIP.
If your cat is showing FIP in cats symptoms, please take them to your nearest veterinarian for proper diagnosis and treatment.
And if you have any questions or concerns about FIP and its treatment, please do not hesitate to reach out to us on Facebook or visit our Instagram to get in touch with our expert team.
Frequently Asked Questions about GS-441524 & EIDD-1931
What is the difference between GS-441524 and EIDD-1931 for treating FIP?
GS-441524 has been the main antiviral treatment for FIP for years, while EIDD-1931 is a newer option. Both target viral replication but have different chemical properties, treatment forms, and clinical experience behind them.
Which treatment is more effective for FIP in cats?
Current clinical use suggests GS-441524 offers higher and more consistent success rates, especially with wet and dry FIP. EIDD-1931 is still under evaluation in many regions but may offer an alternative when GS is unavailable.
Can I switch from EIDD-1931 to GS-441524 if my cat doesn't respond?
In some cases, transitioning between treatments is possible, depending on your cat's response and your vet’s guidance. Always consult a professional before making any changes.
Are both GS-441524 and EIDD-1931 safe for long-term treatment?
Both compounds are antivirals with promising safety profiles in FIP cases when used correctly. The key to safety is dosage accuracy, quality sourcing, and veterinary supervision.
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