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Does Famvir (famciclovir) cause side effects?
Famvir (famciclovir) is a nucleoside analog antiviral drug active against the Herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes) and varicella-zoster (shingles and chickenpox).
Famvir relieves pain, burning, itching, and tingling, and also heals and prevents sores associated with herpes infections. It stops the spread of herpes virus in the body by preventing the replication of viral DNA that is necessary for viruses to multiply.
Famvir is actually a "prodrug," that is, not active directly against viruses. Instead, Famvir is converted to penciclovir in the body, and it is the penciclovir that is active against the viruses.
Famvir is active against the same viruses as acyclovir but has a longer duration of action. Therefore, it can be taken fewer times each day. Famvir does not cure or stop the spread of herpes infections.
Common side effects of Famvir include
Serious but rare side effects of Famvir include
- serious allergic reactions,
- serious skin reactions,
- yellowing skin and eyes (jaundice),
- abnormal liver function tests,
- reduced white blood cells (neutropenia) or platelets (thrombocytopenia), and
- kidney failure when higher than recommended doses are administered to patients with underlying kidney problems.
What are the important side effects of Famvir (famciclovir)?
The most common side effects associated with the use of famciclovir are:
Other important side effects which are serious, but rare, include
- serious allergic reactions,
- serious skin reactions,
- 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.
Famvir (famciclovir) side effects list for healthcare professionals
Acute renal failure is discussed in greater detail in other sections of the label.
The most common adverse events reported in at least 1 indication by >10% of adult patients treated with Famvir 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.
The safety of Famvir has been evaluated in active-and placebo-controlled clinical studies involving
- 816 Famvir-treated patients with herpes zoster (Famvir, 250 mg three times daily to 750 mg three times daily);
- 163 Famvir-treated patients with recurrent genital herpes (Famvir, 1000 mg twice daily);
- 1,197 patients with recurrent genital herpes treated with Famvir as suppressive therapy (125 mg once daily to 250 mg three times daily) of which 570 patients received Famvir (open-labeled and/or double-blind) for at least 10 months; and
- 447 Famvir-treated patients with herpes labialis (Famvir, 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 Famvir Trials*
|Events||Herpes Zoster†||Recurrent Genital Herpes‡||Genital Herpes-Suppression§||Herpes Labialis‡|
|Body as a Whole|
|Skin and Appendages|
|*Patients may have entered into more than one clinical trial.
†7 days of treatment
‡1 day of treatment
Table 3 lists selected laboratory abnormalities in genital herpes suppression trials.
Table 3 Selected Laboratory Abnormalities in Genital Herpes Suppression Studies*
|Anemia (<0.8 x NRL)||0.1||0.0|
|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|
|*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.
- 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%).
The adverse events listed below have been reported during postapproval use of Famvir. 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
- Immune system disorders: Anaphylactic shock, anaphylactic reaction
- Nervous system disorders: Dizziness, somnolence, seizure
- 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, angioedema (e.g., face, eyelid, periorbital, and pharyngeal edema), hypersensitivity vasculitis
- Cardiac disorders: Palpitations
What drugs interact with Famvir (famciclovir)?
Potential For Famvir To Affect Other Drugs
- The steady-state pharmacokinetics of digoxin were not altered by concomitant administration of multiple doses of famciclovir (500 mg three times daily).
- No clinically significant effect on the pharmacokinetics of zidovudine, its metabolite zidovudine glucuronide, or emtricitabine was observed following a single oral dose of 500 mg famciclovir coadministered with zidovudine or emtricitabine.
- An in vitro study using human liver microsomes suggests that famciclovir is not an inhibitor of CYP3A4 enzymes.
Potential For Other Drugs To Affect Penciclovir
- No clinically significant alterations in penciclovir pharmacokinetics were observed following single-dose administration of 500 mg famciclovir after pretreatment with multiple doses of allopurinol, cimetidine, theophylline, zidovudine, promethazine, when given shortly after an antacid (magnesium and aluminum hydroxide), or concomitantly with emtricitabine.
- No clinically significant effect on penciclovir pharmacokinetics was observed following multiple-dose (three times daily) administration of famciclovir (500 mg) with multiple doses of digoxin.
- Concurrent use with probenecid or other drugs significantly eliminated by active renal tubular secretion may result in increased plasma concentrations of penciclovir.
- The conversion of 6-deoxy penciclovir to penciclovir is catalyzed by aldehyde oxidase.
- Interactions with other drugs metabolized by this enzyme and/or inhibiting this enzyme could potentially occur.
- Clinical interaction studies of famciclovir with cimetidine and promethazine, in vitro inhibitors of aldehyde oxidase, did not show relevant effects on the formation of penciclovir.
- Raloxifene, a potent aldehyde oxidase inhibitor in vitro, could decrease the formation of penciclovir.
- However, a clinical drug-drug interaction study to determine the magnitude of interaction between penciclovir and raloxifene has not been conducted.
Famvir (famciclovir) is a nucleoside analog antiviral drug active against the Herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes) and varicella-zoster (shingles and chickenpox). Common side effects of Famvir include headache, fatigue, nausea, vomiting, rash, diarrhea, and gas (flatulence). Famvir has not been adequately studied in pregnant women. It is unknown if Famvir is excreted into breast milk.
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Second Source article from Government
Shingles, or herpes zoster, is a painful rash caused by the varicella zoster virus. Other shingles symptoms include headache, fever, nausea, and body aches. Treatment focuses on pain management and shortening the duration of the illness with antiviral medications.
Genital Herpes in Women (Symptoms, Signs, Treatment)
Genital herpes is a sexually transmitted disease (STD) caused by the herpes simplex virus (HSV). Symptoms of genital herpes include painful blisters and often fever, body aches, and swollen lymph nodes for first time infection. Genital herpes is diagnosed with lab tests to test for the presence of the virus. Treatment for genital herpes includes antiviral medications to shorten the duration of the outbreak or reduce the risk of future outbreaks. There is no cure for genital herpes. Condoms may help prevent the spread of genital herpes.
Cold Sores (Nongenital Herpes Simplex Infections)
Herpes simplex infections are common and when they appear around the mouth and lips, people often refer to them as "cold sores" and "fever blisters." Canker sores are different than cold sores. Air droplets can spread the virus, as can direct contact with the fluid from the blisters. Cold sore treatment include over-the-counter medication, as well as prescription medications.
Herpes of the eye occurs due to herpes simplex virus-1 (HSV-1). Symptoms of herpes of the eye include pain in and around the eye, rash or sores on the eyelids, redness, swelling, and cloudiness of the cornea.
Shingles and Pregnancy
Becoming infected with chickenpox during pregnancy could cause birth defects in your unborn child. Likewise, shingles could also cause problems for your unborn child. If you are pregnant and haven't had chickenpox, avoid exposure to infected people. Zostavax, the shingles vaccine, can reduce the incidence of shingles by half. Women should wait at least three months after receiving the vaccine before trying to get pregnant.
Is Shingles Contagious?
Shingles is an infection caused by the varicella-zoster virus. Shingles symptoms and signs include skin burning, numbness, and tingling along with a painful red, blistering rash. Shingles is contagious until all of the blisters have crusted over.
Are Cold Sores (Fever Blisters) Contagious?
About 20% of cases of cold sores are caused by herpes simplex virus type 2 (HSV-2), and approximately 80% of cold sores are caused by herpes simplex virus type 1 (HSV-1). Cold sores are transmitted by sharing utensils and razors, kissing, and oral sex. There is no cure for cold sores.
Pimple vs. Cold Sore
Pimples are areas of skin inflammation with pus in the center. Cold sores are fluid-filled blisters. Pimples are caused by bacterial overgrowth and inflammation. Cold sores are caused by infection with herpes simplex viruses (HSV-1 and HSV-2). Benzoyl peroxide and sometimes antibiotics treat acne. Antiviral medications accelerate the healing process of oral herpes.
What Causes You to Get Shingles?
Shingles (herpes zoster) is caused by varicella zoster virus, the same virus that causes chickenpox. Sometimes, in patients with a history of chickenpox, the virus may live in the nervous system for years in an inactive form, and then reactivate as shingles.
How Long Is Shingles Contagious?
Shingles is contagious from the time the blisters are oozing until the time the blisters have scabbed.
What Does a Shingles Rash Look Like at First?
The typical shingles red rash or blisters occur after pain, itching, and tingling. They are usually limited to one side of the face and body.
Can You Have a Mild Case of Shingles?
The severity of shingles depends on various factors, such as age of the patient, general health condition of the patient, and the part of the body where shingles develops.
What Triggers Herpes?
Once a person is infected with herpes, the virus may stay dormant or quiet within the nerves. It is not known what exactly may trigger the symptoms.
5 Things You Should Know About Herpes
Most people who have genital herpes have no symptoms or have very mild symptoms. Patients may not notice mild symptoms or may mistake them for another skin condition, such as a pimple or ingrown hair.
What Can Trigger a Cold Sore?
After you get infected with HSV, it lies inactively in the nerve cells inside your skin and may appear as another cold sore at the same place as before.
Do Cold Sores Mean You Have an STD?
Having a cold sore does not necessarily mean you have an STD. Most of the cold sores are caused by herpes simplex virus type 1 (HSV-1), which usually affects the lips and is not generally transmitted by sexual contact.
What Are the Symptoms and Signs of Herpes?
Herpes is a type of infection caused by the herpes simplex virus (HSV). It causes sores or blisters to form in or around the mouth or genitals.
Are Cold Sores and Canker Sores the Same Thing?
Although cold sores and canker sores have similarities, they are entirely different conditions. Canker sores are not contagious, but cold sores are. Canker sores show up inside the mouth, while cold sores are often seen on the lips.
Do I Have a Cold Sore or Canker Sore?
Having a cold sore or canker sore is painful and differentiating them isn’t always easy. However, a cold sore isn’t the same as a canker sore. Cold sores are usually caused by the herpes virus and it is highly contagious. Canker sores are mouth ulcers that are not contagious.
What Does Herpes Look Like? Types and Treatment
Herpes is a skin infection caused by herpes simplex virus (HSV). It results in the formation of painful blisters or sores on the skin, typically around the mouth or genitals.
Genital Herpes and Cold Sores: 10 Myths and Facts
Genital herpes and cold sores (oral herpes) are the names given to two types of infection caused by the two types of herpes simplex virus (HSV): HSV-1 and HSV-2.
How Do I Get Rid of a Cold Sore Overnight?
You cannot get rid of cold sores overnight. There is no cure for cold sores. However, to speed up the healing time of a cold sore, you can consult with your doctor and take prescription medications such as antiviral tablets and creams. A cold sore may go away without treatment within a week or two.
Treatment & Diagnosis
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- Shingles Pain
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- Can the Chicken Pox Vaccine Cause Shingles?
- Is Herpes During Pregnancy Dangerous to the Baby?
- Can Stress Cause Shingles?
- Shingles Contagious Period and Diagnosis
- Shingles Prevention: Who Should Get the Vaccine?
- Shingles During Pregnancy
- Shingles Treatment
- Cold Sore Treatment
- Shingles Symptoms and Signs
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Medications & Supplements
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.