Detailed Drug Information:

DRUG CLASS AND MECHANISM: Famciclovir is an antiviral drug whichis active against the Herpes viruses, including herpes simplex 1 and 2(cold sores and genital herpes) and varicella-zoster (shingles and chickenpox). It inhibits the replication of viral DNA that is necessary in orderfor viruses to reproduce themselves. Famciclovir is actually a "prodrug,"in that it is not active directly against viruses. Instead, famciclovir isconverted to penciclovir in the body, and it is the penciclovir that isactive against the viruses. (Penciclovir also is available as a topicaland intravenous medication.) Famciclovir is active against the sameviruses as acyclovir but has a longer duration of action. Therefore, itcan be taken fewer times each day. Famciclovir was approved for use by theFDA in 1994.

PREPARATIONS: Tablets (125mg, 250mg, 500mg).

STORAGE: Famciclovir should be kept between 2° and 30°C(36-86° F).

PRESCRIBED FOR: Famciclovir is used to treat the first episodeof genital herpes and to treat patients with recurrent (more than 6episodes per year) severe genital herpes. Famciclovir reduces the pain andthe number of sores with the first episode and decreases the frequency andseverity of episodes in individuals with recurrent episodes. In thetreatment of shingles, famciclovir reduces pain, shortens the time inwhich sores heal, and limits the spread of virus and the formation of newsores. Famciclovir can be used to treat chicken pox to reduce healingtime, limit the number of sores (pox), and reduce fever if used within thefirst 24 hours after the onset of the disease.

DOSING: Famciclovir may be taken with or without food.Penciclovir, the active metabolite of famciclovir, is excreted mainly bythe kidney, and dosages of famciclovir need to be reduced in patients withkidney dysfunction.

DRUG INTERACTIONS: Probenecid (Benemid) may reduce the kidney'sclearance of penciclovir leading to higher concentrations of penciclovirin the blood. This may lead to side effects of penciclovir. Usingfamciclovir with digoxin (Lanoxin) may result in an increase in theconcentration of digoxin in the blood. This may lead to side effects ofdigoxin.

PREGNANCY: Animal studies have not produced effects on thefetus. However, there have been no studies in humans. Famciclovir shouldonly be used during pregnancy when the benefits to the mother outweighpotential risks to the fetus.

NURSING MOTHERS: Studies in rats have shown higher concentrations of penciclovir in breast milk than in blood. It is notknown if penciclovir is excreted into human milk. Women may wish toconsider an alternative to breast-feeding if famciclovir is taken whilenursing.

SIDE EFFECTS: The most common side effects associated with theuse of famciclovir are headache, fatigue, nausea, and vomiting. Lesscommon side effects include fever, pain, shaking chills, constipation,loss of appetite, abdominal pain, back pain, joint pain, dizziness,tingling of the extremities, tiredness, sore throat, sinus congestion, anditching.