Famir (Famciclovir) is used for the treatment of genital herpes and cold sores in adult patients with normal immune systems and also for HIV-infected individuals with a compromised immune system. It also is approved for treating shingles (herpes zoster) in adults with normal immune systems. To be most effective, famciclovir should be started as soon as possible after the diagnosis of a herpes infection.
Famciclovir is an antiviral drug which is active against the Herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes) and varicella-zoster (shingles and chickenpox). It belongs to a class of drugs called nucleoside analogs that mimic one of the building blocks of DNA. It stops the spread of herpes virus in the body by preventing the replication of viral DNA that is necessary for viruses to multiply. Other drugs in the same class include acyclovir (Zovirax) and valacyclovir (Valtrex). Famciclovir is actually a “prodrug,” that is, not active directly against viruses. Instead, famciclovir is converted to penciclovir in the body, and it is the penciclovir that is active against the viruses. Famciclovir is active against the same viruses as acyclovir but has a longer duration of action. Therefore, it can be taken fewer times each day. Famciclovir does not cure or stop the spread of herpes infections. Famciclovir relieves pain, burning, itching, and tingling, and also heals and prevents sores associated with herpes infections.
What is the recommended dose? Famciclovir may be taken with or without food. The recommended doses are:
Recurrent genital herpes: 1,000 mg every 12 hours for one day.
Recurrent cold sores: 1,500 mg as a single dose.
Suppression of recurrent genital herpes: 250 mg twice daily.
Shingles: 500 mg every 8 hours for 7 days.
HIV-infected patients (cold sores or genital herpes): 500 mg twice daily for 7 days.
DRUG INTERACTIONS: Probenecid (Benemid) may reduce the kidney’s removal of famciclovir leading to higher concentrations of famciclovir in the blood. This may lead to side effects from famciclovir.
PREGNANCY: Famciclovir has not been adequately studied in pregnant women.
NURSING MOTHERS: It is not known if famciclovir is excreted into human breast milk. Women may wish to consider an alternative to breastfeeding if famciclovir is taken.
SIDE EFFECTS: The most common side effects associated with the use of famciclovir are headache, fatigue, nausea, vomiting, rash, diarrhea, and flatulence. Serious but rare side effects include serious allergic reactions, serious skin reactions, jaundice, abnormal tests of liver function, and reduced white blood cells (neutropenia) or platelets (thrombocytopenia). Cases of kidney failure have been reported when higher than recommended doses of famciclovir were administered to patients with underlying kidney problems.