Famciclovir is a prodrug that, once absorbed by the cat's body, is transformed into the active metabolite, penciclovir, which acts by inhibiting viral replication by blocking a component of the viral nucleic acid that is essential in replication, so the virus is reduced or prevented from multiplying and, therefore, continuing to affect the cat and produce symptoms. In cats, it is used in the treatment of feline rhinotracheitis caused by feline herpesvirus type 1, a disease that affects cats of all ages, but can be more serious in kittens, and that also causes ocular and respiratory signs. nonspecific symptoms such as fever, anorexia, or depression. Fortunately, it is a disease that has a vaccine, included in the trivalent or triple feline virus along with others that act against important viruses in cats: feline calicivirus and feline panleukopenia virus.
What is famciclovir?
Famciclovir is a active ingredient from the group of guanine analog antivirals, one of the nitrogenous bases that contains the nucleic acid of the virus and that is necessary for its correct replication and that it continues to act on the cat's organism. It is an active ingredient used in human medicine against herpes-type viruses. In cats, it has been shown that inhibits the replication of feline herpesvirus type 1, responsible for feline rhinotracheitis, being the indicated treatment for this disease.
Famciclovir is not a drug itself, but a prodrug, since, once absorbed, it is metabolized to BRL42359 and subsequently it is oxidized to penciclovir, the active metabolite that will actually perform the antiviral action on feline herpesvirus type 1 in infected cats.
What is famciclovir used for in cats?
Famciclovir is used as an antiviral to control the symptoms and progression of feline herpesvirus type 1 in cases of feline rhinotracheitis In addition to stop viral spread, can help in the symptomatic treatment of conjunctivitis, fever, secretions and sneezing that characterize this viral respiratory process in small felines.
The name of the drug that contains famciclovir and is used in cats to control this virus is called Famvir® and is located in tablet format This is a use that is not contemplated, since there is no drug marketed for cats that contains this prodrug and the marketed and approved one must be used by the FDA for the human species.
How does feline herpesvirus type 1 work?
Feline herpesvirus type 1 is a double-stranded DNA virus that has the ability to remain dormant in the cells of infected cats, being able to reactivate under immunosuppressive or stressful conditions. It is easily spread through nasal, pharyngeal or eye secretions, as well as through the hands or clothes of people who carry the virus on them because they have previously petted or been in contact with an infected cat.
Cats affected with this disease show respiratory signs, ocular signs(ulcers, keratitis, corneal sequestrations, hyperemia and secretions) and nasal (serous or mucopurulent discharge, sneezing). They also have signs of illness such as depression, anorexia, or fever. In kittens, this infection can be particularly serious, and can end in sudden death due to pneumonia and uncontrollable viremia. For more details, don't miss our article on Feline Rhinotracheitis.
In addition to famciclovir, other drugs with antiviral effect such as trifluridine, idoxuridine, vidarabine have also been used to treat this disease, cidofovir, acyclovir, ganciclovir, lysine and interferons, the latter also act as immunomodulators.
Famciclovir dose for cats
Several studies have been conducted in recent years evaluating different doses of famciclovir in cats for the treatment of this virus, obtaining that dosages of 30, 40 or 90 mg/kg two or three times a day reduced symptoms and viral load. In this sense, the effect is faster and more effective at doses of 90 mg/kg/12h or 40 mg/kg/8h, the former being more comfortable because the treatment has to be applied twice a day and not three.
In kittens or cats with kidney disease, the indicated dose is 62.5 mg/cat/24h. The treatment is usually around 3 weeks, although it can be extended if necessary. In any case, it is essential that the veterinarian recommends administering famciclovir to the sick cat.
Contraindications and side effects of famciclovir in cats
Famciclovir should not be used in very sick cats and pregnant and lactating cats, as well as in cats allergic to any of the drug's excipients.
Famciclovir side effects in cats
Famciclovir can have side effects in cats, like any medication. The most common side effects that we can expect after the use of famciclovir are the following:
- Loss of appetite
- Polyuria (urinating more)
- Nausea
- Vomiting
- Diarrhea
- Disorientation
- Drowsiness
If these adverse effects do not appear, it is essential to consult the veterinarian in charge of the case to discuss what has happened.
