What It Is:
Famciclovir is an antiviral medication used in cats to treat feline herpesvirus type 1 (FHV-1), which causes upper respiratory infections and eye problems. It is the only oral antiviral commonly prescribed for cats with this virus and is especially helpful for cats with chronic or recurring flare ups.
Famciclovir is not FDA approved for veterinary use, but it is widely used off label in feline medicine with positive results and a good safety profile.
🐾 What It Treats
Famciclovir is used to manage symptoms of feline herpesvirus, including:
- Sneezing and nasal discharge
- Eye discharge or conjunctivitis
- Keratitis (corneal inflammation)
- Ulcers on the cornea
- Recurring respiratory flare ups in stressed or immunocompromised cats
- Chronic upper respiratory infections related to FHV-1
It does not cure the virus, but it reduces symptoms and shortens the duration of flare ups.
🧪 How It Works
Famciclovir is converted in the body to penciclovir, which interferes with the virus’s ability to replicate its DNA. This stops the virus from spreading and gives the body time to recover.
It is most effective when given early during a flare up, and may be prescribed long term in severe or chronic cases.
🐾 Dosage and Administration
Famciclovir is usually prescribed as oral tablets, though some compounding pharmacies offer it in liquid form for easier dosing.
General guidelines:
- Given two to three times daily, depending on severity
- Dosage varies widely by weight, condition, and tolerance
- May be given with or without food
- Always use the veterinary dose — human tablets may require splitting or compounding
Never adjust the dose without veterinary approval, as underdosing can make it less effective and overdosing can cause side effects.
🔍 Side Effects and Precautions
Famciclovir is generally safe for most cats. Possible side effects include:
- Mild gastrointestinal upset
- Vomiting or diarrhea
- Lethargy or reduced appetite
- Increased liver enzymes in rare cases
Use with caution in cats with:
- Kidney disease (may need a lower dose)
- Liver disease
- Known sensitivity to antiviral drugs
Let your vet know about any other medications or supplements your cat is taking before starting famciclovir.
🩺 Prognosis
Famciclovir does not cure herpesvirus, but it is highly effective for symptom relief:
- Many cats improve within a few days of starting treatment
- May be used as needed during flare ups, or daily for long term management
- Works best when combined with stress reduction and supportive care
With proper use, famciclovir helps reduce discomfort, prevent complications, and improve quality of life for cats with FHV-1.
💡 Cat Owner Note
Feline herpesvirus is something your cat may carry for life, but that doesn’t mean they have to suffer. Famciclovir gives you a powerful way to take control of flare ups and protect your cat’s eyes, nose, and comfort. Keep it on hand if flare ups are common, and talk to your vet about a long term plan.
❓ Frequently Asked Questions About Famciclovir for Cats
Does famciclovir cure feline herpesvirus?
No. It does not cure the virus, but it reduces symptoms and speeds recovery during flare ups.
How long should my cat take famciclovir?
It depends. Some cats take it for a few days, others need long term or ongoing treatment for chronic symptoms.
Can I give my cat leftover human famciclovir?
No. Human doses are too high and may not be accurate for cats. Always use a veterinary prescribed dose.
What if I miss a dose?
Give it as soon as possible, but do not double up. Resume the normal schedule afterward.
Can I give it with food?
Yes. Famciclovir can be given with or without food, depending on what your cat tolerates best.
What other treatments help with feline herpesvirus?
Supportive care such as L-lysine supplements, humidifiers, eye drops, and reducing stress can all help manage symptoms.