Petco Text Logo
Petco Pet Logo

  • Two Easy Ways to Start Earning Rewards!

My cat accidentally got a double dose of Famciclovir. Is she okay?

Updated On September 23rd, 2025

Pet's info: Cat | Mixed Breed | Female | spayed | 16 years and 5 months old | 11 lbs

My cat was given a 125 mg dose of Famciclovir at the veterinary clinic at 5:30 pm. I brought this cat home after being boarded overnight and accidentally gave her another 125 mg dose of this medicine at 6:30 pm. She has eaten three small meals since I gave her the additional dose, but has not used the litter box. Have I accidentally harmed her? What should I do? I love her dearly. She seems ok.

3 Answers

Most Helpful Answer

Image profile

Answered By Destini R. Holloway, DVM

Veterinarian

Published on June 19th, 2017

According to the veterinary medicine resource this drug has been tolerated at doses up to 90 mg/kg with mild symptoms (anorexia and excessive drinking) in some cats. Callie would have to have eaten 450 mg of Famciclovir to see these symptoms, so she is well below this amount if she ingested 2-125mg tablets totaling 250mg. She should be fine, however you can also consult with pet poison helpline to talk it over with a certified toxicologist as well. But based on my minimal research she is below the toxic level for ingestion. I hope your sweet girl continues to do well. Take care.

Vote icon

2Pet Parents found this answer helpful

Other Answers

  • Image profile

    Answered By Christie Long, DVM

    Veterinarian, Certified Veterinary Acupuncturist

    Published on

    Knowing Callie's weight would help to determine whether this is a harmful dose. The most commonly followed published dose for famciclovir is 40 milligrams per kilo of body weight every 8 hours. If Callie weighs 10 pounds (average for adult cats) that means that her dose would be around 180 milligrams every 8 hours. If the dose given at the vet clinic was the first of the day, and you gave the second dose (both at 125 mg) I think you have not harmed her. Research shows that at doses of 90 milligrams per kilo, cats showed decreased or absent appetite, and increased thirst. Your dosage wasn't close to that. Monitor, but I suspect she will be fine. You can also call the ASPCA's poison control hotline ((888) 426-4435) for any additional information they may have regarding famciclovir overdoses. There is a fee for their services.

    Vote icon

    1Pet Parents found this answer helpful

  • Image profile

    Answered By Dr. Melanie, BVSc MS

    Veterinarian

    Published on November 9th, 2019

    Thank you for contacting Petco Pet Education Center, formerly Petcoach with your question about Charlie. This may be ok. This can be dosed at 40 to 90mg/kg in cats, and even if he did have 125mg, that is still within the normal dose range. You don't need to do anything. I hope this helps!

    Vote icon

    1Pet Parents found this answer helpful

See More Answers

Related Questions

Petco Pet Education Center
Health & Wellbeing
What fish dog food helps dry skin if my dog eats Science Diet?
Is your dog's dry skin a concern? A certified vet offers expert advice on finding the best fish-based dog food alternatives to Science Diet for essential oils.
Updated on February 04, 2026
Petco Pet Education Center
Food & Nutrition
What's the best way to feed my hamster when I'm going on a trip?
Planning a trip to Chicago and need to feed your Syrian hamster? A certified vet offers expert advice on feeding options for short and long trips, plus finding trusted pet sitters.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
Can chickens eat bell peppers daily and what about veggie salads?
Can your chickens eat bell peppers and salads? Veterinarian Dr. Elizabeth offers expert advice on safe feeding, frequency, and how fresh veggies boost vibrant yolks.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
Is Purina Layer Pellets good for chickens? What other feeds exist?
Is Purina Layer Pellets the right choice for your flock? Get expert advice from a Petco veterinarian on Purina and other top chicken feed brands for your chickens.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
My newly adopted pet won't eat hay. What can I do to encourage it?
Adopted a pet not eating hay? Dr. Stafford, a certified vet, offers expert guidance on encouraging hay consumption, including adjusting pellets and trying fresh types.
Updated on December 04, 2025
Petco Pet Education Center
Food & Nutrition
My mice eat all their food together from one bowl. Is this normal?
Do your mice quickly eat together from one bowl? A Licensed Vet Tech explains normal mouse eating behavior and when to watch for aggression. Get expert insights.
Updated on December 04, 2025
image
Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Book Now

Sponsored