QUARTERLY BEAT
JULY 2026
remdesivir is still advisable with the goal of transitioning to oral GS-441524 once able. While data on oral absorption (especially when complicated by various gastrointestinal conditions) is lacking, current recommendations are to give oral GS-441524 on an empty stomach and wait 30 minutes before a full meal - but hiding a crushed tablet in a small treat is still considered ok! Update #2: Treatment Duration may be Effective in a Shorter (6 week) Course in SOME Cats Most FIP protocols still include a 12-week treatment plan, often with once daily GS-441524 administration for 84 days (or split q12h if neuro/ocular disease is in the mix). That said, newer data looking at cats with ‘wet’ FIP show that many did well with a 6-week course without incurring a higher relapse risk. The catch? This shorter course was studied only in cats that presented mostly with an effusive FIP form, had been diagnosed early in their disease, were treated early as a result, and were hospitalized for their first week of treatment. The study used oral GS-441524 at 15 mg/kg q24h and found most of these cats had a fast response to treatment with resolution of lab work abnormalities and elevated alpha-1 acid glycoprotein (AGP) levels, often within the first 28 days. But before shortening your patients’ treatment, be sure to prioritize a response-driven approach.
BLOG HIGHLIGHTS
In 2026, nucleoside analogues remain the backbone of FIP therapy, and treatment protocols continue to evolve with clinical experience, emerging studies, and (in some regions) improved access to quality-assured drugs. In areas where legal access is limited, some veterinarians and cat owners have turned to unregulated products — often out of necessity. VETgirl echoes International Cat Care’s caution: black-market antivirals may have inconsistent active drug content, no quality assurance, and have been associated with adverse events, including reports of severe injection-site injuries linked to highly acidic formulations. And while none of us want to play “antiviral roulette,” if limited access guides your antiviral selection, just remember the goal is to treat thoughtfully, monitor patient’s closely, and give that cat a fighting chance. With that context in mind, the current backbone of FIP treatment are the nucleoside analogue antivirals, which work by interfering with feline coronavirus RNA replication. This group includes GS-441524, remdesivir, molnupiravir, and EIDD-1931 (with legal access varying by country and, in some regions, requiring a compounding pharmacy). Molnupiravir and its parent drug EIDD-1931 carry additional safety considerations such as reported neutropenia, potential viral mutation concerns, and teratogenic risk, so they’re typically reserved as backup options for treatment failures or relapses, or for regions where access to GS-441524 and/or remdesivir is limited. Beyond nucleoside analogues, there are emerging successful reports using nirmatrelvir with ritonavir (Paxlovid™) in refractory or neurologic cases. Lastly, GC-376, a 3CL protease inhibitor, has gained attention from anecdotal reports, but its restricted access puts it in the “watch for now” category. Next, we break down some of the major highlights and pearls we’ve learned so far in our treatment battle against FIP. Update #1: Oral GS-441524 can be First-line Therapy From Day 1 We no longer need to start with injectable antivirals (i.e., remdesivir), unless the patient is severely dehydrated, cannot swallow, or otherwise cannot receive oral medications. But for critically ill or clinically dehydrated patients, hospitalization for ~48 hours for IV fluid therapy and injectable Wondering what’s changed in FIP treatment? This VETgirl article , article walks through the current antiviral lineup, emphasizes thoughtful monitoring (and fast pivots when cats aren’t improving), and reviews dosing considerations for the tricky ocular/neuro patients. Read on for practical guidance on what drugs to reach for, how long to treat, and what responses should we expect to see throughout treatment. And if you’d prefer instead to listen about FIP diagnostic updates, you can also tune into our FIP in Real Practice- Updated Clinical Cues and Diagnostics podcast HERE ! FIP IN REAL PRACTICE – UPDATED CLINICAL CUES AND DIAGNOSTICS Dr. Amy Kaplan-Zattler , cVMA, DACVECC, MRCVS CE Program Manager, VETgirl
Practical rule of thumb: Treat at least 2 weeks past normalization of biochemistry abnormalities and AGP levels, as well as resolution of effusion/ocular/neuro signs. We don’t want our haste to be the reason a cat relapses!
Update #3: Follow a Streamlined Dosing Framework by FIP “Type” (with Special Attention to Eyes and Brains)
Ocular and neurologic presentations generally warrant dose adjustments to improve penetration across the blood-brain/blood-CSF and blood- ocular barriers. Dose increases may improve penetration, and dividing the total dose into twice-daily administration may maintain steadier blood concentrations throughout the day. Below are suggested antiviral doses by clinical signs, and extrapolated from icatcare.org.
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