Famvir Side Effects

Generic name: famciclovir

Note: This document contains side effect information about famciclovir. Some of the dosage forms listed on this page may not apply to the brand name Famvir.

Some side effects of Famvir may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to famciclovir: oral tablet

Get emergency medical help if you have any of these signs of an allergic reaction while taking famciclovir (the active ingredient contained in Famvir) hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Stop using famciclovir and call your doctor at once if you have a serious side effect such as:

• urinating less than usual or not at all;

• weakness, confusion, increased thirst, loss of appetite, vomiting, pounding heartbeats or fluttering in your chest; or

• swelling, weight gain, feeling short of breath.

Less serious side effects of famciclovir may include:

• nausea, gas, stomach pain;

• diarrhea,

• headache, tired feeling;

• dizziness, sleepiness;

• mild itching or skin rash; or

• numbness or tingly feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.

For Healthcare Professionals

Applies to famciclovir: oral tablet

General

Famciclovir (the active ingredient contained in Famvir) is generally well tolerated. The most common side effects reported in at least 1 indication by greater than 10% of patients are headache and nausea.

Gastrointestinal

An isolated case of acute necrotic-hemorrhagic pancreatitis occurred in a kidney graft recipient who was treated with famciclovir (the active ingredient contained in Famvir) for severe hepatitis B infection. The author could not identify any other etiologic factor for the pancreatitis, although some possible predisposing factors were noted, including the patient's liver insufficiency and renal dysfunction.

Gastrointestinal side effects have included nausea (up to 13%), diarrhea (up to 9%), vomiting (up to 5%), flatulence (up to 4.8%), abdominal pain (up to 7.9%), elevated amylase (greater than 1.5 times normal range high [NRH]; 1.5%) and lipase (greater than 1.5 times NRH; 4.9%), dyspepsia, and anorexia. Pancreatitis has been reported rarely.

Nervous system

Confusion and bradykinesia developed in an 80-year-old woman who received famciclovir (the active ingredient contained in Famvir) for acute herpes zoster. The dosage administered was clinically appropriate and adjusted to her estimated creatinine clearance. Although herpes zoster may sometimes elicit neurological complications and cannot be ruled out as a contributing factor, the patient's mobility problems and mental deterioration corresponded temporally with drug administration (onset within 48 and 72 hours, respectively, of initiation and reinstitution of therapy).

Nervous system side effects have included headache (up to 39.3%), paresthesia (up to 2.6%), migraine (up to 3.1%), and insomnia. Dizziness and somnolence have been reported during postmarketing experience.

Dermatologic

Dermatologic side effects have included pruritus (up to 3.7%) and rash (up to 3.3%). Urticaria, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, and angioedema (e.g., face, eyelid, periorbital, and pharyngeal edema) have been reported during postmarketing experience.

Hematologic

Hematologic side effects have included anemia (less than 0.8 times normal range low [NRL]; 0.1%), leukopenia (less than 0.75 times NRL; 1.3%), and neutropenia (less than 0.8 times NRL; 3.2%). Thrombocytopenia has been reported during postmarketing experience.

Hepatic

Hepatic side effects have included elevated AST (greater than 2 times NRH; 2.3%), ALT (greater than 2 times NRH; 3.2%), and total bilirubin (greater than 1.5 times NRH; 1.9%). Cholestatic jaundice and abnormal liver function tests have been reported been reported during postmarketing experience.

Genitourinary

Genitourinary side effects have included dysmenorrhea (up to 7.6%).

Other

Other side effects have included fatigue (up to 4.8%), injury, back pain, viral infection (including influenza, flu-like symptoms, and symptoms of a cold), asthenia, and fever.

Renal

Renal side effects have included elevated serum creatinine (greater than 1.5 times NRH; 0.2%) and acute renal failure.

Psychiatric

Psychiatric side effects have included confusion (including delirium, disorientation, and confusional state occurring predominantly in the elderly), and hallucinations during postmarketing experience.

Respiratory

Respiratory side effects have included upper respiratory tract infection and pharyngitis.

Hypersensitivity

Hypersensitivity side effects have included leukocytoclastic vasculitis.

Oncologic

Oncologic side effects have included increase in incidence in mammary adenocarcinoma in female rats receiving high dose famciclovir (the active ingredient contained in Famvir) (600 mg/kg/day) and dose-related testicular atrophy in male rats, mice, and dogs following repeated administration of famciclovir following animal studies. Famciclovir had no reproductive or fertility effects in rats at doses up to 1000 mg/kg/day.

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