Molnupiravir 101: What to Know About Using Molnupiravir to Treat Infectious Peritonitis in Cats (FIP)

Molnupiravir is an antiviral medication designed primarily to treat mild to moderate COVID-19 in humans. However, clinical studies have demonstrated that it can also serve as an off-label rescue therapy for cats suffering from Feline Infectious Peritonitis (FIP) both as a first line of treatment and as a secondary line of treatment when GS-441524 has been shown to be ineffective. We note that Wedgewood’s formulation containing molnupiravir has not been studied in any clinical trials. Wedgewood makes no claims of safety or efficacy with respect to the medications it produces and sells. The information provided herein is for informational purposes only.

Molnupiravir is not currently FDA-approved for cats. The dosing ranges recommended by veterinarianary researchers go from 10mg/kg to 20mg/kg, given twice daily for 84 days, depending on the specific type of FIP: Effusive, Non-Effusive, Neurological or Ocular.

Molnupiravir interferes with the FIP virus enzymes and biological processes. Veterinarians may also recommend adding an immunosuppressive treatment, like prednisolone, to reduce inflammation. Studies state that molnupiravir is a safe and effective option for FIP, typically requiring a 12-week treatment period to eliminate the virus. Dosing may change based on the cat's weight and response to treatment, particularly as the cat successfully regains weight after starting the medication.

Molnupiravir is generally well tolerated. Cats being treated may experience:

• Folded ears
• Broken whiskers
• Diarrhea
• Hives, itching, skin rash, redness of the skin
• Nausea
• Vomiting
• In dosages above 23 mg/kg twice daily, severe leukopenia (lower-than-normal number of white blood cells) is possible.

Molnupiravir dosing varies from 10mg/kg, 12mg/kg, 15mg/kg, and 20mg/kg – two times per day based on the type of FIP – Effusive, Non-Effusive, Neurological, or Ocular.

The dosage forms and strengths below are the most common prepared by Wedgewood.

View all Molnupiravir options

If the cat misses a dose, give the next dose as soon as possible or, if it is close to the next scheduled dose, return to the regular schedule. Do not give two doses (double dose) to catch up. If owners are not sure what to do, they should call their veterinarian and follow their directions.

Molnupiravir is generally well tolerated. Symptoms of an overdose of molnupiravir include:

• Severe nausea, vomiting, and diarrhea
• Severe leukopenia (lower-than-normal number of white blood cells) is possible.

Owners should contact their veterinarian immediately if they suspect an overdose.

If you suspect your cat or another animal has accidentally overdosed or has eaten this medication inadvertently, immediately contact your veterinarian or the A.S.P.C.A.’s Animal Poison Control Center at 888-426-4435.

If you or someone else has ingested this medication, call the National Capital Poison Center at 800-222-1222.

Veterinarians prescribe a specific dosage based on the cat’s weight, condition, and other factors. Compounded medications are prepared for the exact strength veterinarians prescribe. The price of the medication will depend on the dosage and the medication form, with certain dosage forms and higher strengths generally being more expensive. 

Is molnupiravir better than GS-441524 for FIP in cats?

Research shows that molnupiravir can work both as a first-line rescue therapy as well as a secondary line of therapy when symptoms persist or relapse after initially treating with GS-441524.

Is molnupiravir FDA-approved for cats?

The FDA has not approved molnupiravir for animal use but has authorized it for human treatment of mild to moderate COVID-19 in high-risk patients. However, multiple studies suggest it's a safe and effective option for treating FIP in cats.

Can my practice order molnupiravir for office use?

Molnupiravir was nominated to the FDA’s list of office stock drugs and is currently under review, per GFI #256. This means that molnupiravir can be sold to hospitals for office use in all states except Hawaii, Montana, New York, Oregon, Rhode Island, South Dakota, and Washington D.C. Veterinarians who work in a state that does not allow USP compounded medications for office use can prescribe molnupiravir in a patient’s name.

How long will it take for an order or prescription for molnupiravir to ship, and how long will it spend in transit?

Orders for molnupiravir are expected to ship within 1-2 business days. Time in transit will depend on the shipping method chosen.

Do you ship internationally?

We ship to all 50 states, Puerto Rico, the US Virgin Islands, Guam, and all US military bases worldwide.

What is the Beyond-Use Dating (BUD) for molnupiravir?

The oral liquids will have a 90-day BUDs from the date of compounding. The capsules will have 180 days from the day of compounding.

Where can I find more information?

Molnupiravir treatment of 18 cats with feline infectious peritonitis: A case series

Unlicensed Molnupiravir is an Effective Rescue Treatment Following Failure of Unlicensed GS-441524-like Therapy for Cats with Suspected Feline Infectious Peritonitis

*The medications used in the studies were not provided by Wedgewood Pharmacy and we make no claim that the results found in the studies have any connection with or relevance to the results that may be achieved with any Wedgewood Pharmacy drug. The authors of these studies are not endorsing in any manner any Wedgewood Pharmacy product and any implication to the contrary is expressly denied.