TREATMENT PROTOCOL — Protocol
A standard protocol, by form
and symptoms.
The dosing protocol recommended by FIP Support optimizes dosage and duration according to the dry and wet
forms. The content of this page is treatment guidance; actual dosage should follow the final judgment of a
veterinarian.
Standard treatment flow
Five steps from diagnosis to completion of treatment
01
Diagnosis & severity assessment
Blood tests, ultrasound, symptom review, and assessment of effusion characteristics
02
Initial treatment: injection
Intensive treatment with the injection (20 mg/ml); at least one week is recommended
03
Transition to oral
Once the condition is stable, switch to oral treatment with tablets
04
Adjustment & observation
Adjust dosage according to symptoms and response; monitor with regular testing
05
Treatment complete
Usually 84 days for both the dry and wet forms (not shortened even if remission is seen)
DRY TYPE — Dry form
Dry form injection dose
Using a 6 ml vial, 20 mg/ml
Standard dose (per kg body weight)
0.6 – 0.8ml / kg
Cases with neurological or ocular signsSEVERE 0.8 – 1.0 ml/kg (not reduced even as the cat improves)
Daily tablet dose by weight (oral phase)
Up to 2.0 kg
1 tab
/ day (once daily)
Up to 4.0 kg
2 tab
/ day (once daily)
As a baseline, 1 tablet per 2 kg of body weight. Kittens under 1 kg: 0.5 tablet. For over 4 kg or
intermediate weights, adjust at the veterinarian's discretion. Re-weigh weekly and recalculate on
current body weight.
Main indications & severe symptoms
Hind-limb weakness (unsteadiness, difficulty standing) / neurological symptoms (seizures, circling, etc.) / ocular lesions (uveitis, clouding of the eye)
WET TYPE — Wet form
Wet form injection dose
Using a 6 ml vial, 20 mg/ml
Recommended dose (per kg body weight)
0.52 – 0.60ml / kg
1.3–1.5× the former reference of 0.4 ml/kg. Where a purely wet form is confirmed, 0.4 ml/kg may still be used
Daily tablet dose by weight (oral phase)
Up to 2.0 kg
0.75 tab
3/4 tablet / day
Up to 4.0 kg
1.5 tab
/ day (once daily)
As a baseline, 0.75 tablet per 2 kg of body weight (1.5× the former 0.5). Kittens under 1 kg: 3/8 tablet
(round up to 1/2 if splitting is impractical). For over 4 kg or intermediate weights, adjust at the
veterinarian's discretion. Re-weigh weekly and recalculate on current body weight.
Key points for setting the dose
Most cases in practice are mixed wet-and-dry, so the reference dose assumes the mixed form / adjust while checking effusion reduction and overall condition / transition to oral after effusion decreases and the condition stabilizes / do not reduce the dose for apparent weight loss caused by effusion resorption
CO-MEDICATION — Combination therapy
Recommended combination therapy for both forms
Rather than antiviral medication alone, combining it with anti-inflammatory and organ-protective measures can
improve the prognosis.
Required
Anti-inflammatory drugs
To suppress inflammation from vasculitis and granulomas, always use in combination. Use for about 10 days from the start of treatment as a guide, and avoid long-term continuous use. Because oxidative stress in the body is thought to remain high even after 10 days, also consider antioxidant supplements (vitamin E, CoQ10, SAMe, glutathione, resveratrol, broad-spectrum CBD, etc.).
Prednisolone
Steroids
NSAIDs
Recommended
Liver protectants / supplements
To reduce the burden on the liver from long-term treatment, we recommend combining where possible. Monitor with regular blood tests during the treatment period.
SAMe (liver support)
Vitamin E
CoQ10
Glutathione
Resveratrol
Broad-spectrum CBD
CRITICAL POINTS — Operation & management
Key points common to both forms
i.
Transition from injection to tablets
Through the unstable early phase (at least about one week), injections reliably maintain blood concentration; switch to tablets once the condition stabilizes. In cases with neurological or ocular signs, continue injections until those signs have fully resolved.
ii.
Individual adjustment by symptoms
The doses shown are guidelines. The veterinarian flexibly adjusts dose and duration according to symptom improvement and changes in body weight.
iii.
Owner adherence
Because treatment is long (84 days as standard, longer for neurological or ocular cases), maintaining the owner's motivation and reliable daily dosing is important. If an owner asks to reduce the dose because the cat looks better, explain the risk of relapse.
CRITICAL — When neurological or ocular signs are present
Do not reduce or stop on apparent recovery.
Improvement in general condition does not mean healing inside the brain and eyes.
Where neurological or ocular signs are involved, maintain the higher dose
(equivalent to 0.8–1.0 ml/kg by injection) and complete the full course.
01
Why it matters: the drug barely reaches
Because of the blood-brain barrier, GS-441524 reaches only about 7–21% of plasma concentration
in the brain and eyes. Resolving effusion, a normalised A:G ratio, and returning appetite show
improvement outside the brain and eyes — they cannot rule out residual virus within them.
02
Three common pitfalls
Switching to oral too early (oral absorption is under 50% of injection, so the same
stated dose delivers roughly half) / reducing on apparent recovery (concentration in
the brain falls with it) / ignoring weight gain (holding the dose steady is an
unnoticed reduction).
03
Rules of thumb
Maintain the higher dose and never reduce part-way / continue injections until neurological signs
have fully resolved, then move to oral / weigh weekly and recalculate the dose on current body
weight (increase as the cat grows).
If the disease relapses
Reset the 84-day count and restart with injections at a higher dose than before (a guide is +5 mg/kg).
A minimum of eight weeks is recommended (Pedersen, UC Davis).
Key sources: Pedersen et al. 2019 (JFMS) / Dickinson et al. 2020 (JVIM) / Pedersen, UC Davis treatment summary / ISFM (Taylor et al.) 2025 / JFMS Open Reports 2025
Note: measured brain and intraocular concentrations come from only a handful of cases, and systematic pharmacokinetic data in affected cats do not exist. That is precisely why not lowering an unmeasurable brain concentration on the basis of apparent recovery is the safer course.
SUMMARY — Protocol comparison
Dry form / Wet form / Neuro-ocular summary
| Item |
Dry form |
Wet form |
Neuro / ocular signs |
| Initial injection period |
at least 1 week |
at least 1 week |
until signs fully resolve |
| Recommended injection dose |
0.6 ml/kg |
0.52 – 0.60 ml/kgmixed form assumed |
0.8 – 1.0 ml/kg |
| Injection dose range |
0.6 – 0.8 ml/kgup to 1.0 with neuro/ocular signs |
0.4 only if purely wet |
no reduction on improvement |
| Oral tablet reference60 mg / tablet |
1 tablet per 2 kgunder 1 kg: 0.5 |
0.75 tablet per 2 kgunder 1 kg: 3/8 |
1 tablet per 2 kgafter signs resolve |
| Oral tablet by weightonce daily |
≤2 kg: 1 / ≤4 kg: 2 |
≤2 kg: 0.75 / ≤4 kg: 1.5 |
≤2 kg: 1 / ≤4 kg: 2 |
| Total treatment period |
usually 84 days |
usually 84 dayscomplete even if remission |
84 days or longeruntil criteria are met |
KEY TAKEAWAYS
1
Set the dose by form
and symptoms (84-day course)
2
Combine with anti-inflammatory
and liver-protective drugs
3
Observe continuously and
adjust the plan as needed
⚠ Disclaimer
Actual dosage and duration are determined by the veterinarian based on the individual's symptoms and test results.
If injecting the cat is difficult, a tablet-only approach is also possible. This page is treatment guidance and is
not a substitute for medical judgment.