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A PRACTICAL PROTOCOL FOR CAT GUARDIANS

Molnupiravir for Feline Stomatitis.

Complete treatment guide — including pre-treatment checks, dosage calculations, concurrent medications, supplements, and bloodwork monitoring.

14 min total read

6 chapters · evidence-based

Before starting treatment.

Before day one of Molnupiravir, three things must be done first: a dental examination, baseline oral photos, and strict isolation. Skipping these preparations is one of the most common reasons treatment fails.

3 MIN READ

1. Get a full dental X-ray.

A full dental X-ray is recommended before starting treatment or during the treatment course. Many cats with FCGS also suffer from aggressive periodontal disease, tooth resorption, retained roots, or severe dental infections. These lesions can continuously trigger local inflammation and immune dysregulation, which may interfere with stomatitis treatment. If damaged teeth are present, proper dental treatment should be performed first.

2. Document the mouth with photos.

Take clear "before" photos of both sides of the mouth and the back of the throat. Flash on, same angle every time. Repeat monthly so you and your vet can compare objectively.

3. Strictly isolate your cat.

If there are other cats in the household, isolation during treatment is strongly recommended. One of the main causes of feline stomatitis is chronic calicivirus infection, and even cats that appear completely healthy may still be silent carriers of feline calicivirus (FCV). Calicivirus can also spread through the air. Isolation is the best way to help prevent long-term viral carriage and reinfection in cats with stomatitis.

⚠ For shelters and rescue organizations: a cat receiving treatment must be strictly isolated from other cats. In multi-cat environments, the treatment failure rate is significantly higher than in single-pet households.

Gradually taper symptom-control medications.

Improvement can usually be observed within 3–4 days after starting Molnu treatment. Once the condition begins to improve, pain medications and antihistamines should be gradually reduced and discontinued under veterinary supervision.

2 MIN READ

3–4

DAY 3 — 4

First signs of improvement.

What to expect

Reduced drooling
Better appetite
Less mouth pawing
Returning to favourite spots

↓

ONCE STABLE

Begin tapering.

Under vet supervision

Reduce painkiller dose stepwise
Lower antihistamines gradually
Watch for relapse cues
Adjust if symptoms return

Dosing protocol.

Enter your cat's weight and the calculator will return the correct capsule fraction. Re-calculate any time your cat's weight changes by more than 0.5 kg.

1 MIN READ

Dosage Calculator

Dose by body weight

Cat's weight

Recommended capsule

—

Enter a weight to begin

Standard dose reference

Capsule fraction per dose · follow your vet's frequency

Weight range	Capsule
2 – 3.4 kg	⅕ capsule
3.5 – 4.4 kg	¼ capsule
4.5 – 5.4 kg	⅓ capsule
5.5 – 6.4 kg	⅖ capsule
6.5 – 7.5 kg	½ capsule

How to give it

Once you have the right capsule fraction, follow these rules.

🕑

Twice daily, 12 hours apart

8–14 hour intervals are acceptable if 12 h isn't practical.

⚖️

Re-check when weight changes

If your cat gains or loses more than 0.5 kg, run the calculator again.

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Mix powder into food

Open the capsule, mix powder into strongly-flavoured wet food (Churu works well). Make sure it's fully blended so the dose isn't lost.

Concurrent medications.

Molnu primarily targets the virus itself. To bring inflammation under control more quickly, two short-term supportive treatments are usually recommended alongside it: antibiotics and low-dose corticosteroids. Both medications require a prescription from a veterinarian.

3 MIN READ

Medication

Why & what to prescribe

Antibiotics
(top picks)

Doxycycline or Metronidazole. These medications not only help suppress bacteria, but also have known immune-modulating effects.

Antibiotics
(alternative)

Amoxicillin-Clavulanate. A solid backup if doxycycline or metronidazole isn't suitable for your cat.

Corticosteroid

Prescribed at the lowest effective dose for FCGS. FCGS starts as chronic viral infection → immune dysregulation → bacterial overgrowth → runaway inflammation. Antivirals + antibiotics ease off the accelerator; steroids hit the brake.

All courses typically run 1–2 months · adjust under veterinary supervision.

IN SHORT

You can think of the immune dysregulation in stomatitis as a car with the accelerator stuck down. Molnu and antibiotics release the gas pedal — cutting off the viral and bacterial triggers that keep inflammation out of control. Corticosteroids press the brake — suppressing the overactive immune response. Using both together in the short term helps bring the runaway inflammation back under control.

Recommended supplements.

Two categories work best in parallel: a local oral treatment (sprays that target the gum surface directly) and systemic support (probiotics, lactoferrin, NAC + glycine, and optionally vitamin D).

4 MIN READ

REQUIRED · LOCAL ORAL CARE

Antimicrobial oral spray.

Choose at least one (ideally two) oral sprays for your cat and use them according to the product instructions.

Look for products containing these active ingredients:
• Chlorhexidine
• Zinc gluconate
• Zinc acetate

REQUIRED · SYSTEMIC

Anti-inflammatory & immune support.

Probiotics and lactoferrin are non-negotiable; NAC + glycine are strongly recommended.

• NAC: 50–70 mg/kg, once daily
Must be paired with glycine
• Glycine: 50–70 mg/kg, once daily
Must be paired with NAC
• Probiotics containing Lactobacillus plantarum and L. acidophilus
• Lactoferrin: 20 mg/kg, once daily

OPTIONAL · VITAMIN D

Test before you supplement.

Most stomatitis cats have low vitamin D, but supplement only after a blood test confirms it. Over-supplementation is dangerous.

Test ordered by your vet:
25-Hydroxy Vitamin D (LC-MS/MS)

Healthy range: 90–120 ng/mL

If deficient: 16–20 IU/kg, once daily

Blood monitoring & dose adjustments.

Molnupiravir is generally well tolerated, but it can still potentially cause some side effects, such as leukopenia, anemia, and elevated ALT levels.

2 MIN READ

Bloodwork schedule

① MONTH 1

Baseline + month-one check

Full CBC (complete blood count) + basic biochemistry.

② EVERY 2 MONTHS

If month-one was normal

Repeat CBC + biochem every 2 months for the rest of the course.

⚠ IF ABNORMAL

If anemia or leukopenia occurs

Treatment should be paused for 1–2 weeks and bloodwork switched to monthly monitoring. Please inform us — we'll provide recommendations based on your situation.

Do this

Order baseline bloodwork before starting, so you have a comparison point if something shifts later.
Recalculate the dose whenever your cat's weight changes by more than 0.5 kg.
Stick to a 12-hour rhythm if possible. 8–14 hour intervals are still acceptable.
Photograph the mouth monthly with flash, both sides + back of throat, for objective progress tracking.
Keep your vet looped in at the month-one CBC and at each milestone.

Don't do this

Don't stop the protocol the moment your cat seems "back to normal" — relapses come back harder after early discontinuation.
Don't supplement vitamin D without a confirmed blood result — over-dosing can damage kidneys.
Don't skip the dental X-ray on cats that still have teeth — undiagnosed dental disease quietly sabotages the course.
Don't share Molnu courses between cats. Each dose is calculated for an individual weight.
Don't drop antibiotics or steroids cold-turkey — taper under your vet's supervision.

FREQUENTLY ASKED

Questions guardians ask most.

If you don't see your question here, reach out — we answer every message within one business day.

01 When will I see the first signs of improvement?

Most cats show clear improvement within 3–4 days of starting Molnupiravir — reduced drooling, better appetite, less pawing at the face. Visible reduction in oral inflammation typically follows in week 3–4. Full healing requires completing the entire course; don't stop early.

02 My cat's weight is between table rows. Which dose do I use?

Use the formula: 17 mg × weight (kg). The table is a quick reference, but the formula always wins. A ±10 mg tolerance is acceptable. Re-calculate any time your cat's weight changes by more than 0.5 kg.

03 Do I really need to do the dental X-ray and the bloodwork?

Yes — both are essential. Undiagnosed dental disease keeps the inflammation alive no matter how much antiviral you give. And the month-one CBC + biochem is how your vet catches the rare bone-marrow or organ effect before it becomes a problem (the fix is simple: drop to 15 mg/kg and monitor monthly).

04 Can I skip isolation if I only have one cat at home?

In a single-cat household, you don't need to "isolate" your cat from anyone — there's no one to isolate from. The isolation rule applies to multi-cat homes, shelters, and rescues, where other cats may be silent calicivirus carriers and re-infect your patient mid-treatment.

05 My cat is improving — can I stop the painkillers?

You can taper them, not stop overnight. Once your vet confirms the Molnu has clearly kicked in (usually after 1–2 weeks of steady improvement), they'll reduce painkillers and antihistamines in steps over a couple of weeks. Cold-turkey stopping can cause rebound inflammation that obscures whether the treatment is actually working.

06 Do I have to supplement vitamin D?

Only if a blood test (25-OH Vitamin D via LC-MS/MS) shows your cat is below the 90–120 ng/mL healthy range. Most stomatitis cats are low, but supplementing without testing is risky — vitamin D over-dose damages kidneys. If you're confirmed deficient, the dose is 16–20 IU/kg daily.

READY TO START

Your cat's treatment journey deserves expert guidance.

Download the full PDF guide for offline reference, or talk with our team about whether the PETCOME protocol is right for your cat.

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