Feline Infectious Peritonitis, effusive · By mouth
Feline Infectious Peritonitis, non-effusive · By mouth
Feline Infectious Peritonitis, ocular · By mouth
Feline Infectious Peritonitis, neurological · By mouth
Any weight
10–15 mg/kg
15 mg/kg
15–20 mg/kg
15–20 mg/kg
Feline Infectious Peritonitis, effusive · By mouth (every 12 hours, for 84 days): The vet chooses each dose in this range; nothing is filled in. Off-label: a human medicine; dose from Core molnupiravir (Reagan 2024), same substance and route. Effusive FIP: 10-15 mg/kg; a 4 kg cat needs 40-60 mg, about a quarter of this 200 mg capsule. THE CAPSULE HAS TO BE OPENED and the powder divided or compounded into smaller doses (off-label; the label says not to open it, and the cat studies used compounded doses). Wear gloves and keep away from pregnant handlers (possible mutagen). Guidelines prefer GS-441524 where available and advise caution above 15 mg/kg every 12 hours. Not registered in Georgia.
Feline Infectious Peritonitis, non-effusive · By mouth (every 12 hours, for 84 days): Off-label: a human medicine; dose from Core molnupiravir (Sase 2023), same substance and route. Non-effusive FIP without ocular or neurological signs: 15 mg/kg; a 4 kg cat needs 60 mg, about a third of this 200 mg capsule. THE CAPSULE HAS TO BE OPENED and the powder divided or compounded into smaller doses (off-label; the label says not to open it, and the cat studies used compounded doses). Wear gloves and keep away from pregnant handlers (possible mutagen). Guidelines prefer GS-441524 where available and advise caution above 15 mg/kg every 12 hours. Not registered in Georgia.
Feline Infectious Peritonitis, ocular · By mouth (every 12 hours, for 84 days): The vet chooses each dose in this range; nothing is filled in. Off-label: a human medicine; dose from Core molnupiravir (Sase 2023; FelineVMA 2025), same substance and route. Ocular FIP: 15-20 mg/kg; a 4 kg cat needs 60-80 mg, a third to two fifths of this 200 mg capsule. THE CAPSULE HAS TO BE OPENED and the powder divided or compounded into smaller doses (off-label; the label says not to open it, and the cat studies used compounded doses). Wear gloves and keep away from pregnant handlers (possible mutagen). Guidelines prefer GS-441524 where available and advise caution above 15 mg/kg every 12 hours. Not registered in Georgia.
Feline Infectious Peritonitis, neurological · By mouth (every 12 hours, for 84 days): The vet chooses each dose in this range; nothing is filled in. Off-label: a human medicine; dose from Core molnupiravir (Sase 2023; FelineVMA 2025), same substance and route. Neurological FIP: 15-20 mg/kg; a 4 kg cat needs 60-80 mg, a third to two fifths of this 200 mg capsule. THE CAPSULE HAS TO BE OPENED and the powder divided or compounded into smaller doses (off-label; the label says not to open it, and the cat studies used compounded doses). Wear gloves and keep away from pregnant handlers (possible mutagen). Guidelines prefer GS-441524 where available and advise caution above 15 mg/kg every 12 hours. Not registered in Georgia.
Source:
JVIM 2024 (10 cats)
Scientific article
A study or review published in a scientific journal. Its findings apply to the animals and conditions it studied.
Open label clinical trial of orally administered molnupiravir as a first-line treatment for naturally occurring effusive feline infectious peritonitis
Journal of Veterinary Internal Medicine 38:3087-3094, 2024
Feline Infectious Peritonitis · By mouth: No dog dose: no label, consensus or study gives a dog treatment dose. In safety studies bone marrow toxicity appeared at 17 mg/kg a day or more (no-effect level 6 mg/kg a day); do not use the cat dose in dogs.
Source:
Lagevrio SmPC
Official product label (SPC), MHRA, UK
Approved by the UK Medicines and Healthcare products Regulatory Agency (MHRA) as part of the product's authorisation. It applies to that product as authorised there.
Lagevrio 200 mg hard capsules - Summary of Product Characteristics
Dog: no treatment dose exists, and the cat dose must not be transferred. In the safety studies, bone marrow toxicity affecting all blood cell lines appeared at 17 mg/kg a day or more (no-effect level 6 mg/kg a day), with thrombocytopenia and haemorrhage; recovery was partial or full depending on the dose. The usual cat dose is 20-40 mg/kg a day.
Source: EMA Sources: Lagevrio SmPC · FDA · EMA · PubMed
Warning
Do not use in pregnant or lactating animals or animals intended for breeding. In the human label, embryo-fetal death and malformations (eye, kidney, axial skeleton) occurred in rats at 8 times the human exposure, and reduced fetal weight in rabbits; the active metabolite reached nursing pups.
Sources: Lagevrio SmPC · FDA
Warning
Young animals: in young rats it thickened growth cartilage and impaired its change into bone at 500 mg/kg a day or more (5-6 times the human exposure). No such effect was seen in dogs; the meaning for kittens is not known.
Source: EMA Sources: Lagevrio SmPC · FDA · EMA
Warning
Handling: wear gloves; pregnant people should not handle it. The human label says not to open the capsule; cat doses need the powder divided or compounded (off-label). Bacterial mutation tests were positive and one animal test equivocal, while the other animal tests were negative; the human label's low-risk statement refers to a 5-day course, and cat courses run 84 days.
Sources: Lagevrio SmPC · FDA
Warning(Cat)
Cat (off-label): raised liver enzymes (ALT) and gastrointestinal signs are the most reported. Neutropenia and occasional anaemia occur at higher doses, with severe leukopenia reported above 23 mg/kg; folded ears and hair or whisker loss are also reported. Guidelines advise caution above 15 mg/kg every 12 hours and keep it second-line to GS-441524.
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