Famciclovir Side Effects

Brand Names: Famvir

Please note - some side effects for Famciclovir may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Famciclovir - for the Consumer

Famciclovir

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Famciclovir:

Diarrhea; gas; headache; nausea; stomach pain; tiredness; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); change in the amount of urine produced; confusion; delirium; disorientation; hallucinations; red, swollen, blistered, or peeling skin; unusual bruising or bleeding; yellowing of the eyes or skin.

Famciclovir Side Effects - for the Professional

Famciclovir

Immunocompetent Patients

The safety of Famciclovir has been evaluated in clinical studies involving 816 Famciclovir-treated patients with herpes zoster (Famciclovir, 250 mg t.i.d. to 750 mg t.i.d.) and 1,197 patients with recurrent genital herpes treated with Famciclovir as suppressive therapy (125 mg q.d. to 250 mg t.i.d.) of which 570 patients received Famciclovir (open-labeled and/or double-blind) for at least 10 months. Table 5 lists selected adverse events.

Table 6 lists selected laboratory abnormalities in genital herpes suppression trials.

HIV-Infected Patients

In HIV-infected patients, the most frequently reported adverse events for Famciclovir (500 mg twice daily; n = 150) and acyclovir (400 mg, 5x/day; n = 143), respectively, were headache (16.7% vs. 15.4%), nausea (10.7% vs. 12.6%), diarrhea (6.7% vs. 10.5%), vomiting (4.7% vs. 3.5%), fatigue (4.0% vs. 2.1%), and abdominal pain (3.3% vs. 5.6%).

Postmarketing Experience

The following adverse events have been reported during post-approval use of Famciclovir: urticaria, serious skin reactions (e.g., erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), cholestatic jaundice, abnormal liver function tests, thrombocytopenia, hallucinations, dizziness, somnolence and confusion (including delirium, disorientation, confusional state, occurring predominantly in the elderly). Because these adverse events are reported voluntarily from a population of unknown size, estimates of frequency cannot be made.

Side Effects by Body System

General

Famciclovir is generally well tolerated. Gastrointestinal and nervous system adverse effects were most commonly reported in clinical trials in immunocompetent patients.

Gastrointestinal

An isolated case of acute necrotic-hemorrhagic pancreatitis occurred in a kidney graft recipient who was treated with famciclovir 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 (2.2% to 13%), diarrhea (1.8% to 9%), vomiting (1.2% to 4.8%), flatulence (0.6% to 4.8%), abdominal pain (1.1% to 7.9%), elevations in amylase (1.5%) and lipase (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 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 (9.7% to 39.3%), paresthesia (0.9% to 2.6%), migraine (0.7% to 3.1%), dizziness, somnolence, and insomnia. Hallucinations, confusion, delirium, and disorientation have also been reported, occurring predominantly in the elderly.

Hematologic

Hematologic side effects have included anemia (0.1%), leukopenia (1.3%), neutropenia (3.2%), and thrombocytopenia.

Hepatic

Hepatic side effects have included elevations in AST (2.3%), ALT (3.2%), and total bilirubin (1.9%). Cholestatic jaundice and abnormal liver function tests have been reported been reported during postmarketing experience.

Dermatologic

Dermatologic side effects have included pruritus (up to 3.7%) and rash (up to 3.3%). Urticaria and serious skin reactions (including erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis) have been reported during postmarketing experience.

Genitourinary

Genitourinary side effects have included dysmenorrhea (0.9% to 7.6%).

Other

Other side effects have included fatigue (0.6% 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 elevations in serum creatinine (0.2%).

Oncologic

Oncologic side effects have included increase in incidence in mammary adenocarcinoma in female rats receiving high dose famciclovir (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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