Famciclovir (Famvir) has been around for a while as a treatment for feline herpesvirus infection. Until now, though, we haven’t really known how much to use, or how often. A new study has some answers.
First, though – when should we consider using Famvir? It’s not always straightforward. If there is severe stress and overcrowding, URI can be severe and difficult to resolve, regardless of what treatment is used. The other catch is that, in experimental studies, investigators treat a known infection involving one pathogen. In shelters, we are often treating two or more organisms, and we usually don’t know which ones are present in an individual cat.
That said, if the clinical signs are consistent with FHV, there’s a really good chance the cat does have it – simply because it’s such a common infection, particularly in shelters.
According to Koret Shelter Medicine, Famvir should be considered in severe or refractory FHV, or for severe ocular signs (corneal ulcers, severe conjunctivitis). It might also be of some use in chronic rhinosinusitis (Malik 2009), though this was a small and preliminary study. There have even been some recent indications that it might also be helpful for severe calicivirus infections in cats (Cervone 2016).
So, what’s that dose? The new pharmacokinetic study (Sebbag 2016) established that the optimal dose for cats is 90mg/kg twice a day. This mg/kg dose was previously shown to be clinically effective in experimental infections (Thomasy 2011). At 90 mg/kg, it will be a challenge both financially and logistically, but it’s a great tool to have in reserve for severe infections, especially in kittens, which are often hardest hit.
UPDATE: For a more in-depth look at when to use antiviral treatment for feline herpes, and other famciclovir dosage options, visit our follow-up blog here.
References:
- Koret Shelter Medicine Program, URI Information Sheet http://www.sheltermedicine.com/library/resources/feline-upper-respiratory-infection-aka-uri#Treatment
- Malik et al. Treatment of feline herpesvirus-1 associated disease in cats with famciclovir and related drugs. Journal of Feline Medicine and Surgery 2009 11:40-8
- Cervone, Bensignor. Systemic calicivirus infection successfully treated with famciclovir in two cats. Revue Vétérinaire Clinique 2016 51:83-88
- Sebbag et al. Pharmacokinetic modeling of penciclovir and BRL42359 in the plasma and tears of healthy cats to optimize dosage recommendations for oral administration of famciclovir. American Journal of Veterinary Research 2016 77:833-45
- Thomasy et al. Evaluation of orally administered famciclovir in cats experimentally infected with feline herpesvirus type-1. American Journal of Veterinary Research 2011, 72:85–95