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.

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.

Seek medical attention right away if any of these SEVERE side effects occur when using Famciclovir:

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.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

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Famciclovir Side Effects - for the Professional

Famciclovir

Acute renal failure is discussed in greater detail in other sections of the label [see Warnings and Precautions (5)].
 
The most common adverse events reported in at least 1 indication by >10% of adult patients treated with Famciclovir are headache and nausea.

Clinical Trials Experience in Adult Patients

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared with rates in the clinical trials of another drug and may not reflect the rates observed in practice.
 
Immunocompetent patients:  The safety of Famciclovir has been evaluated in active- and placebo-controlled clinical studies involving 163 Famciclovir-treated patients with recurrent genital herpes (Famciclovir, 1000 mg twice daily); 1,197 patients with recurrent genital herpes treated with Famciclovir as suppressive therapy (125 mg once daily to 250 mg three times daily) of which 570 patients received Famciclovir (open-labeled and/or double-blind) for at least 10 months; and 447 Famciclovir-treated patients with herpes labialis (Famciclovir, 1500 mg once daily or 750 mg twice daily). Table 2 lists selected adverse events.

Table 2 Selected Adverse Events (all grades and without regard to causality) Reported by ≥ 2% of Patients in Placebo-Controlled Famciclovir Trials*

Events	Incidence
	Recurrent Genital Herpes‡		Genital Herpes- Suppression§		Herpes Labialis‡
	Famciclovir (n=163) %	Placebo (n=166) %	Famciclovir (n=458) %	Placebo (n=63) %	Famciclovir (n=447) %	Placebo (n=254) %
* Patients may have entered into more than one clinical trial. ‡ 1 day of treatment § daily treatment
Nervous System
Headache	13.5	5.4	39.3	42.9	8.5	6.7
Paresthesia	0	0	0.9	0	0	0
Migraine	0.6	0.6	3.1	0	0.2	0
Gastrointestinal
Nausea	2.5	3.6	7.2	9.5	2.2	3.9
Diarrhea	4.9	1.2	9	9.5	1.6	0.8
Vomiting	1.2	0.6	3.1	1.6	0.7	0
Flatulence	0.6	0	4.8	1.6	0.2	0
Abdominal Pain	0	1.2	7.9	7.9	0.2	0.4
Body as a Whole
Fatigue	0.6	0	4.8	3.2	1.6	0.4
Skin and Appendages
Pruritus	0	0.6	2.2	0	0	0
Rash	0	0	3.3	1.6	0	0
Reproductive (Female)
Dysmenorrhea	1.8	0.6	7.6	6.3	0.4		0

Table 3 lists selected laboratory abnormalities in genital herpes suppression trials.

Table 3 Selected Laboratory Abnormalities in Genital Herpes Suppression Studies*

Parameter	Famciclovir (n = 660)† %	Placebo (n = 210)† %
* Percentage of patients with laboratory abnormalities that were increased or decreased from baseline and were outside of specified ranges. † n values represent the minimum number of patients assessed for each laboratory parameter. NRH = Normal Range High. NRL = Normal Range Low.
Anemia (<0.8 x NRL)	0.1	0
Leukopenia (<0.75 x NRL)	1.3	0.9
Neutropenia (<0.8 x NRL)	3.2	1.5
AST (SGOT) (>2 x NRH)	2.3	1.2
ALT (SGPT) (>2 x NRH)	3.2	1.5
Total Bilirubin (>1.5 x NRH)	1.9	1.2
Serum Creatinine (>1.5 x NRH)	0.2	0.3
Amylase (>1.5 x NRH)	1.5	1.9
Lipase (>1.5 x NRH)	4.9	4.7

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 (17% vs. 15%), nausea (11% vs. 13%), diarrhea (7% vs. 11%), vomiting (5% vs. 4%), fatigue (4% vs. 2%), and abdominal pain (3% vs. 6%).

Postmarketing Experience

The adverse events listed below have been reported during post-approval use of Famciclovir. Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure:

Blood and lymphatic system disorders: Thrombocytopenia

Hepatobiliary disorders: Abnormal liver function tests, cholestatic jaundice

Nervous system disorders: Dizziness, somnolence

Psychiatric disorders: Confusion (including delirium, disorientation, and confusional state occurring predominantly in the elderly), hallucinations

Skin and subcutaneous tissue disorders: Urticaria, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis Top

Side Effects by Body System - for Healthcare Professionals

General

Famciclovir 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 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 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, and toxic epidermal necrolysis 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 (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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