Side effects of acyclovir

Contents

Valacyclovir

Generic Name: valacyclovir (val a SYE kloe veer)
Brand Names: Valtrex

Medically reviewed by Sanjai Sinha, MD Last updated on Jan 14, 2019.

  • Overview
  • Side Effects
  • Dosage
  • Professional
  • Tips
  • Interactions
  • More

What is valacyclovir?

Valacyclovir is an antiviral drug. It slows the growth and spread of the herpes virus to help the body fight the infection.

Valacyclovir is used to treat infections caused by herpes viruses, including genital herpes, cold sores, and shingles (herpes zoster) in adults.

Valacyclovir is used to treat cold sores in children who are at least 12 years old, or chickenpox in children who are at least 2 years old.

Valacyclovir will not cure herpes and will not prevent you from spreading the virus to other people. However, this medicine can lessen the symptoms of an infection.

Important information

Before taking valacyclovir, tell your doctor if you have HIV/AIDS, a weak immune system, kidney disease (or if you are on dialysis), or if you have had a kidney or bone marrow transplant.

Valacyclovir can be harmful to the kidneys, and these effects are increased when it is used together with other medicines that can harm the kidneys. Tell your doctor about all other medications you are using. You may need dose adjustments or special tests when taking certain medications together with valacyclovir.

Treatment with valacyclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Valacyclovir will not prevent the spread of genital herpes. Herpes infections are contagious and you can infect other people even while you are taking this medicine.

Stop taking valacyclovir and call your doctor right away if you have any signs of a serious side effect that can harm red blood cells, such as: fever, easy bruising or bleeding, red spots on the skin (not related to herpes or chickenpox), bloody diarrhea, vomiting, pale or yellowed skin, weakness, fainting, or urinating less than usual or not at all.

Before taking this medicine

You should not use this medicine if you are allergic to valacyclovir or acyclovir (Zovirax).

To make sure valacyclovir is safe for you, tell your doctor if you have:

  • kidney disease (or if you are on dialysis);

  • HIV/AIDS, or other conditions that can weaken the immune system; or

  • a history of kidney transplant or bone marrow transplant.

It is not known whether this medicine will harm an unborn baby. However, herpes virus can be passed from an infected mother to her baby during childbirth. If you have genital herpes, it is very important to prevent herpes lesions during your pregnancy, so that you do not have a genital lesion when your baby is born.

Valacyclovir can pass into breast milk and may harm a nursing baby. Tell your doctor if you are breast-feeding a baby.

Do not give valacyclovir to a child without medical advice.

How should I take valacyclovir?

Take valacyclovir exactly as it was prescribed for you. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Start taking valacyclovir as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). This medicine might not be as effective if you first start taking it 1 or 2 days after the start of your symptoms.

Some herpes infections need to be treated for longer than others. Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely cleared. Skipping doses may increase the risk of your virus becoming resistant to antiviral medicine.

You may take valacyclovir with or without food.

Drink plenty of water while you are taking valacyclovir to keep your kidneys working properly.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

Store valacyclovir tablets at room temperature away from moisture and heat.

What happens if I miss a dose?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking valacyclovir?

Taking this medicine will not prevent you from passing genital herpes to other people. Herpes infections are contagious and you can infect other people even while you are taking with valacyclovir.

Avoid sexual intercourse or use a latex condom to help keep you from spreading the virus to others. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent the spread of infection.

Do not share valacyclovir with another person, even if they have the same symptoms you have.

Valacyclovir side effects

Get emergency medical help if you have signs of an allergic reaction to valacyclovir: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • confusion, aggression, or you feel shaky or unsteady;

  • hallucinations (seeing or hearing things that are not real);

  • problems with speech;

  • a seizure (convulsions); or

  • kidney problems–little or no urination, painful or difficult urination, swelling in your feet or ankles, feeling tired or short of breath.

Stop taking valacyclovir and call your doctor right away if you have any of the following signs of a serious side effect that can harm red blood cells:

  • fever, pale skin;

  • unusual bleeding (nosebleeds, bleeding gums);

  • red or pink urine, little or no urination;

  • red spots on the skin (not related to herpes or chickenpox);

  • feeling weak or tired;

  • stomach pain, bloody diarrhea, vomiting; or

  • swelling in your face, hands, or feet.

Side effects may be more likely in adults who are 65 or older.

Common valacyclovir side effects may include:

  • nausea, stomach pain;

  • headache;

  • rash; or

  • tired feeling.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect valacyclovir?

Valacyclovir can harm your kidneys. This effect is increased when you also use certain other medicines, including: antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).

Other drugs may interact with valacyclovir, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell each of your health care providers about all medicines you use now and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use valacyclovir only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2020 Cerner Multum, Inc. Version: 10.01.

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Shingles treatment and medications

What is shingles? | Shingles diagnosis | Shingles treatment options | Shingles medications | Best shingles medications | Side effects of shingles medication | Living with shingles | FAQ

What is shingles?

Shingles (herpes zoster) is caused by the varicella-zoster virus, which is the same virus that causes chickenpox. Unfortunately, you’re at risk for shingles if you’ve had chickenpox before.

After having chickenpox, this virus may remain dormant for many years before any symptoms of shingles appear. The first sign of shingles is a painful rash, usually on one side of your body or face.

Although preventable by vaccine, shingles is common in the United States. There are more than 200,000 cases of shingles every year. Half of these cases occur in older adults over the age of 60, according to the Centers for Disease Control and Prevention. Symptoms of shingles are treatable, however, the virus is not yet curable.

In this article, we’ll explain the different types of shingles treatment that your healthcare provider may prescribe or recommend, including topical creams, oral medications, the shingles vaccine, and other pain relief tips you can try at home.

How is shingles diagnosed?

Schedule an appointment with your primary care provider or urgent care facility if you experience any symptoms of shingles (most commonly a painful skin rash). You may require immediate medical attention if shingles develops in the eye, if it is widespread across the body, if you’re 60 years old or older, or if you have a weakened immune system from another chronic illness. Consider contacting an ophthalmologist for urgent care as you may be able to get an appointment sooner.

Your primary care provider can diagnose shingles. However, if symptoms appear in the eye, then you might need to see an ophthalmologist.

Shingles can usually be diagnosed with a simple physical exam, as symptoms are usually distinctive. However, if your symptoms are atypical, your doctor may send a tissue scraping or culture from the blisters to the lab for testing. Blood, cerebrospinal fluid, or saliva tests may be necessary if you have nerve pain without a skin rash.

Your healthcare provider may also ask the following questions to help confirm the diagnosis:

  • Have you had chickenpox before?
  • Are you over the age of 60?
  • Have you had the shingles vaccine?
  • Are you stressed?
  • Do you have a chronic illness or are you taking medications (steroids, autoimmune disease medications, antirejection medications for transplant, or chemotherapeutic agents) that could weaken your immune system?

Shingles treatment options

Although some natural solutions and home remedies may help you prevent another shingles episode or alleviate postherpetic neuralgia pain, you should consult your doctor as soon as shingles symptoms appear.

Even though shingles is not completely curable, your doctor will be able to prescribe a medication to relieve your pain and shorten the duration of your symptoms. To get rid of shingles fast, antiviral drugs may alleviate symptoms within three days, according to The National Institutes of Health (NIH).

Shingles medications

Antiviral medication and vaccinations are often the most effective shingles treatments, according to the National Foundation for Infectious Diseases. Here are some of the most popular shingles medications:

Zovirax (acyclovir)

Zovirax is a brand-name prescription drug that’s manufactured by GlaxoSmithKline. Generic acyclovir is also available. It may be prescribed to adults and children at least 12 years of age.

This antiviral medication reduces the severity and duration of shingles episodes. It helps blisters heal faster while preventing new blisters from developing. It also relieves symptoms like burning and itching.

Zovirax (acyclovir) is available as an oral tablet, capsule, or liquid that’s taken up to five times a day. It’s also available as a topical cream that’s applied every three to four hours.

Digestion-related side effects, like nausea, diarrhea, or vomiting, may occur. Headaches are also common.

Valtrex (valacyclovir)

Valtrex is another brand-name medication that’s manufactured by GlaxoSmithKline. The generic version of Valtrex is called valacyclovir. It may be prescribed to adults and children above the age of 12.

Like acyclovir, valacyclovir helps stop the growth of viral infections. It is not a cure for shingles, but it relieves painful symptoms of shingles rashes while preventing new blisters from forming.

It is available as an oral tablet only in the following strengths: 1 gm and 500 mg. Your healthcare provider will determine the right dosage for you depending on your condition, response to treatment, age, and weight. You should drink plenty of water while taking Valtrex (valacyclovir).

Nausea and stomach pain may occur. Valtrex (valacyclovir) might also make you feel lightheaded. Tell your doctor if these side effects continue or worsen.

Famvir (famciclovir)

TEVA Pharmaceuticals manufactures the brand-name drug, Famvir. Famciclovir is the generic version. A doctor may prescribe this medication to adults between the ages of 18 and 65. This may not be the best shingles treatment for patients older than 65 if the patient has renal function problems.

Like the antiviral medications above, Famvir (famciclovir) cannot cure shingles but it can reduce the pain and duration of symptoms. It could also prevent the virus from spreading to other parts of the body.

Famvir (famciclovir) is available as a tablet in strengths of 125 mg, 250 mg, or 500 mg. It is taken by mouth, usually two to three times per day at the first sign of a shingles outbreak.

Common side effects of this antiviral medication include headache, nausea, and diarrhea.

Shingrix

GlaxoSmithKline manufactures the new shingles vaccine called Shingrix. A generic vaccine is not available, as Shingrix was just released in 2017. Most drug patents last 20 years.

Shingrix contains inactivated varicella-zoster, which aids the body’s production of more antibodies than are necessary to fight the virus with a stronger immune system response. As an inactive vaccine, it may be administered to patients with compromised immune systems. It reduces the risk of getting shingles by more than 90% and it’s effective for five years.

Two doses are required for Shingrix to be effective. The second dose should be injected within two to six months of the first dose. Both doses are injected into the muscle. It’s recommended for patients who are at least 50 years old.

Normal side effects include muscle pain, tiredness, fever, and gastrointestinal symptoms. An allergic reaction is possible. Seek emergency medical attention if you experience difficulty breathing, swelling of the face, or severe dizziness.

Zostavax

The Zostavax vaccine was developed by Merck & Co. and approved by the FDA in May 2006. However, it wasn’t approved for use in patients between the ages of 50 and 59 until 2011.

Zostavax contains a live but weakened version of the varicella-zoster virus. Although 19 times stronger than the chickenpox vaccine, Zostavax is less effective than Shingrix. It reduces the risk of shingles by 51% and of prolonged pain by 67%. However, your doctor may prefer that you receive the Zostavax vaccine instead of Shingrix, so consult your healthcare provider for medical advice first.

Only one dose of Zostavax is required. It’s recommended for patients who are at least 60 years old.

Zostavax causes fewer side effects than Shingrix. Injection site reactions are the most common side effect, but a headache, diarrhea, and body aches are also possible. You can get Shingrix at your local pharmacy but be aware this medication is often on backorder and not on the shelves so you may have to shop different pharmacies to see which has Shingrix in stock.

What is the best medication for shingles?

Your healthcare provider will determine the best medication for your case of shingles based on your symptoms, medical history, and response to shingles treatment. Here’s an overview of the popular shingles medications that your doctor may prescribe.

Drug Name Drug Class Administration Route Standard Dosage Side Effects
Zovirax (acyclovir) Antiviral Topical 5% topical cream applied to the affected area every three to four hours Nausea, diarrhea, headache, or vomiting
Zovirax (acyclovir) Antiviral Oral One 400 mg tablet taken two to five times daily Nausea, diarrhea, headache, or vomiting
Valtrex (valacyclovir) Antiviral Oral One one-gram tablet taken at the same time each day as soon as symptoms appear Nausea, stomach pain, headache, or dizziness
Famvir (famciclovir) Antiviral Oral One 500 mg tablet two to three times daily Nausea, diarrhea, or headache
Shingrix (zoster vaccine inactivated) Vaccine Injectable Two 0.5 ml injections that are two to six months apart Muscle aches, headaches, fatigue, or upset stomach
Zostavax (zoster vaccine live) Vaccine Injectable One 0.65 ml injection in the upper arm Irritation of the injection site or chickenpox-like rash near the injection site or headache

Dosage is determined by your healthcare provider based on your medical condition, response to treatment, age, and weight.

Other possible side effects exist. This is not a complete list.

What are common side effects of shingles medication?

Gastrointestinal (GI) side effects are common across shingles medications. These include nausea, diarrhea, upset stomach, and vomiting. It’s important to stay hydrated while taking medications that cause these side effects, as dehydration could be more dangerous than the virus itself.

This is not a full list of side effects. Ask a healthcare professional, such as your physician or pharmacist, for more details regarding the possible side effects of your particular medication.

How can I treat shingles naturally?

The shingles virus affects the nerves, which is why a skin rash only appears in a specific area of the body rather than all over. However, nerve pain is still possible even after the shingles rash has disappeared. If the nerve fibers are damaged, they are unable to send messages from your skin to your brain. This complication of shingles is called postherpetic neuralgia (PHN) and it can cause severe pain, lasting months or even years.

Postherpetic neuralgia is more common in the following patients:

  • Adults over the age of 50
  • Patients with another medical condition, like diabetes
  • Those who experienced a severe shingles rash
  • Those who experienced a shingles rash on the face or torso
  • Patients who didn’t begin shingles treatment within 72 hours of symptoms appearing

Besides chronic pain, symptoms of postherpetic neuralgia include depression, insomnia, suppressed appetite, and attention deficits. Fortunately, there are home remedies, over-the-counter products, and prescription medications that offer pain relief to these symptoms. Here’s a long list of treatments:

  • Taking a cool or lukewarm oatmeal bath can soothe symptoms of itching and burning.
  • Using a cool compress—not an ice pack—can also soothe shingles symptoms, especially herpes zoster ophthalmicus.
  • Applying a natural paste made of baking soda or cornstarch, calamine lotion, capsaicin cream, or lidocaine patch can temporarily relieve skin irritations. However, these topical solutions should be used sparingly, as blistered skin must dry in order to heal.
  • Essential oils, such as St. John’s wort, oregano oil, echinacea, and lemon balm, have antiviral properties.
  • Consuming more citrus fruits, leafy greens, essential fatty acids, and green tea can strengthen the immune system.
  • Taking melatonin before bedtime can help you feel relaxed if you’re having difficulty sleeping.
  • Over-the-counter pain relievers, like Advil (ibuprofen) or Tylenol (acetaminophen), may be used as recommended by your doctor depending on your medical condition.
  • Anticonvulsants, such as Neurontin (gabapentin) can reduce nerve pain.
  • Your primary care provider may also prescribe antibiotics, tricyclic antidepressants (like amitriptyline), corticosteroids, or opioid painkillers depending on your condition.

Frequently asked questions about shingles

How long does shingles last?

The shingles virus lasts a lifetime. However, it may remain inactive for many years at a time. A shingles attack or episode may last between two and four weeks. Here is an average timeline:

  1. Pain begins on a specific area of one side of the body or face.
  2. A red, blotchy rash appears within five days.
  3. The rash blisters. These blisters may merge and form a solid band of inflammation.
  4. New blisters may form throughout a week’s time.
  5. Blisters will eventually dry and scab after seven to 10 days. Minor scarring is possible.

What brings on an attack of shingles?

It’s difficult to predict when a shingles episode might happen again. However, there are some risk factors you should consider.

  • Age
  • Weakened immune system
  • Unhealthy lifestyle
  • Acute on chronic stress

The first risk factor is age. If you are above the age of 50, ask your doctor about the shingles vaccine. In addition to being an effective shingles treatment, this vaccine is used to prevent shingles.

The second risk factor of shingles is immunity. If your immune system is weakened by illness or medication, you are at risk for contracting shingles or experiencing another shingles episode. Fortunately, you can naturally strengthen your immune system with the right diet and vitamins.

Citrus fruits, green vegetables, organic meat, eggs, whole grains, and dairy products are all part of a healthy diet. You should avoid sugar, refined carbohydrates, saturated fat, and arginine-rich foods, like nuts and seeds.

Additionally, take a multivitamin that includes vitamin A, B-12, C, and E. The amino acid lysine is also protective against infection. Many people over the age of 60 are deficient in zinc, selenium, and vitamin D. You may need to incorporate these supplements into your daily routine as well. Ask your healthcare provider for recommendations as to which vitamins and supplements you need.

The third risk factor for shingles is an unhealthy lifestyle. Stress, smoking, and sedentary living can weaken anyone’s immune system and cause a slew of medical conditions. To protect your immune system and prevent another shingles episode, you may have to employ relaxation methods, join a smoking cessation support group, or incorporate more exercise into your everyday life.

How long is shingles contagious?

The varicella-zoster virus is contagious and can be spread from someone who has chickenpox or shingles. Although shingles is a lifelong disease, it is only contagious for some time during each episode. Shingles is contagious from the time your symptoms appear until the time that your blisters have dried or crusted, which usually happens within seven to 10 days of symptoms appearing. As long as the blistered area is covered and hands are clean the spread is contained.

How does shingles spread?

Someone with shingles can pass the virus to someone who hasn’t had chickenpox or shingles before. That person is likely to contract chickenpox first. Then, the virus may reactivate later with symptoms of shingles.

The virus cannot be passed to someone who has already had chickenpox because they already have the virus. If they experience shingles, it’s because they already had the virus—not because they came into contact with you.

You can go to work, school, and other public places with shingles as long as you’re otherwise healthy. However, you should take precautions and keep the shingles rash covered, regularly wash your hands, and avoid at-risk people. Infants, children, pregnant women, and people with weak immune systems are at higher risk for contracting a virus, like shingles, than other people.

How Long is Valacyclovir (Valtrex) in Your System?

Valacyclovir (commonly sold as Valtrex) is one of the most widely used herpes medications on the market. Highly effective at controlling herpes outbreaks, it’s used for everything from HSV-1 and HSV-2, to shingles and chickenpox.

In this guide, we’ll look at how long valacyclovir stays in your system after you take each tablet, as well as the process the drug undergoes inside your body as it converts into aciclovir, its key active ingredient.

Understanding Valacyclovir’s Conversion Process

Valacyclovir is a prodrug, meaning it converts into a different substance once it’s absorbed and metabolized in the body. In the case of valacyclovir, your body will convert it into the active drug acyclovir (or ACV) after it’s absorbed and metabolized.

Acyclovir is itself a powerful antiviral drug that’s highly effective in treating herpes. However, it’s less bioavailable than valacyclovir, meaning that a larger percentage of valacyclovir is absorbed per dose compared to a direct dose of acyclovir.

Because valacyclovir is a prodrug, it’s only active in your body for a short period of time after it’s taken. On its own, its half-life is approximately 30 minutes.

However, once valacyclovir has converted into acyclovir, it has a half-life of 2.5 to 3.3 hours in people with normal renal function.

This means that a single dose of valacyclovir, after conversion into acyclovir by your body, will reduce in concentration every 2.5 to 3.3 hours, staying in your system for a total of about 22 to 25 hours before it’s completely excreted.

Valacyclovir Dosage Guidelines and Usage Periods

Like most antiviral medication, valacyclovir generally isn’t designed to be used as a “one off” treatment for HSV-1 or HSV-2. Instead, most dosage protocols recommend using valacyclovir over the course of several days (often as long as one week) to control a herpes outbreak.

Dosage guidelines for valacyclovir can vary based on the symptoms you’re treating. Generally, valacyclovir usage periods and dosages are more conservative for cold sores and chickenpox than for an initial herpes simplex virus infection.

Our valacyclovir dosages guide includes sample therapeutic protocols for cold sores, genital herpes, shingles, chickenpox and other common conditions that are treated using valacyclovir. And if you want to learn more about valacyclovir in general, check out our Valacyclovir 101 guide, which goes over all the nitty gritty—potential valacyclovir interactions, valacyclovir dosage, how it’s used, what it’s used to treat, where you can buy it, etc.

As always, the best approach to treating any viral infection, including HSV-1 and HSV-2, is to discuss your situation with your doctor and follow the advice they provide.

What You Should Know About Flu Antiviral Drugs

Can flu be treated?

Yes. There are prescription medications called “antiviral drugs” that can be used to treat flu illness. CDC recommends prompt treatment for people who have flu infection or suspected flu infection and who are at high risk of serious flu complications, such as people with asthma, diabetes (including gestational diabetes), or heart disease.

What are antiviral drugs?

Antiviral drugs are prescription medicines (pills, liquid, an inhaled powder, or an intravenous solution) that fight against flu viruses in your body. Antiviral drugs are not sold over-the-counter. You can only get them if you have a prescription from a health care provider. Antiviral drugs are different from antibiotics, which fight against bacterial infections.

What should I do if I think I am sick with flu?

If you get sick with flu, antiviral drugs are a treatment option. Check with your doctor promptly if you are at high risk of serious flu complications (see box below for the full list of high risk factors) and you develop flu symptoms. Flu signs and symptoms can include feeling feverish or having a fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Your doctor may prescribe antiviral drugs to treat your flu illness.

Should I still get a flu vaccine?

Yes. Antiviral drugs are not a substitute for getting a flu vaccine. While flu vaccine can vary in how well it works, a flu vaccine is best way to help prevent seasonal flu and its potentially serious complications. Antiviral drugs are a second line of defense that can be used to treat flu (including seasonal flu and variant flu viruses) if you get sick.

What are the benefits of antiviral drugs?

Antiviral treatment works best when started soon after flu illness begins. When treatment is started within two days of becoming sick with flu symptoms, antiviral drugs can lessen fever and flu symptoms, and shorten the time you are sick by about one day. They also may reduce the risk of complications such as ear infections in children, respiratory complications requiring antibiotics, and hospitalization in adults. For people at high risk of serious flu complications, early treatment with an antiviral drug can mean having milder illness instead of more severe illness that might require a hospital stay. For adults hospitalized with flu illness, some studies have reported that early antiviral treatment can reduce their risk of death.

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When should antiviral drugs be taken for treatment?

Studies show that flu antiviral drugs work best for treatment when they are started within two days of getting sick. However, starting them later can still be beneficial, especially if the sick person is at high risk of serious flu complications or is in the hospital with more severe illness. Follow instructions for taking these drugs.

What antiviral drugs are recommended this flu season?

There are four FDA-approved antiviral drugs recommended by CDC to treat flu this season.

  • oseltamivir phosphate (available as a generic version or under the trade name Tamiflu®),
  • zanamivir (trade name Relenza®)
  • peramivir (trade name Rapivab®), and
  • baloxavir marboxil (trade name Xofluza®).

Generic oseltamivirexternal icon and Tamiflu® are available as a pill or liquid suspension and are FDA approved for early treatment of flu in people 14 days and older. Zanamivir is a powder that is inhaled and approved for early treatment of flu in people 7 years and older. (Note: Zanamivir (trade name Relenza®) is administered using an inhaler device and is not recommended for people with breathing problems like asthma or COPD.) Peramivir is given intravenously by a health care provider and is approved for early treatment of flu in people 2 years and older. Baloxavir is a pill given as a single dose by mouth and is approved for early treatment of flu in people 12 years and older. (Note: Baloxavir (trade name Xofluza®) is not recommended for pregnant women, breastfeeding mothers, outpatients with complicated or progressive illness, or hospitalized patients because there is no information about use of baloxavir in these patients.)

How long should antiviral drugs be taken?

Duration of treatment varies depending on the antiviral drug prescribed. Oseltamivir and zanamivir are usually prescribed to be taken twice daily for 5 days, although people hospitalized with flu may need antiviral treatment for longer than 5 days. Peramivir is given one time intravenously over a period of 15 to 30 minutes. Baloxavir is given as a single oral dose.

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What are the possible side effects of antiviral drugs?

Side effects vary for each medication. The most common side effects for oseltamivir are nausea and vomiting. Zanamivir can cause bronchospasm, and peramivir can cause diarrhea. Other less common side effects also have been reported. Your health care provider can give you more information about these drugs or you can check the Food and Drug Administration (FDA) websiteexternal icon for specific information about antiviral drugs, including the manufacturer’s package insert.

Children and Flu Antiviral Drugs

Parents, if your child gets sick with flu, antiviral drugs offer a safe and effective treatment option. For treatment, influenza antiviral drugs should ideally be started within 2 days after becoming sick and taken for 5 days.

Can children take antiviral drugs?

Yes. Oseltamivir is recommended by CDC and the American Academy of Pediatrics (AAP) for early treatment of flu in people of any age, and for the prevention of flu (i.e., prophylaxis) in people 3 months and older. Zanamivir is recommended for early treatment of flu in people 7 years and older, and for the prevention of flu in people 5 years and older. Peramivir is recommended for early treatment in people 2 years and older. Baloxavir is recommended for early treatment of flu in people 12 years and older.

If your child’s health care provider prescribes oseltamivir capsules for your child and your child cannot swallow capsules, the prescribed capsules may be opened, mixed with a thick sweetened liquid, and given that way. Learn more here.

Can pregnant women take antiviral drugs?

Yes. Oral oseltamivir is recommended for treatment of pregnant women with flu because compared to other recommended antiviral medications, it has the most studies available to suggest that it is safe and beneficial during pregnancy. Baloxavir is not recommended for pregnant women or breastfeeding mothers, as there are no available efficacy or safety data.

Who should take antiviral drugs?

It’s very important that flu antiviral drugs are started as soon as possible to treat hospitalized flu patients, people who are very sick with flu but who do not need to be hospitalized, and people who are at high risk of serious flu complications based on their age or health if they develop flu symptoms. Although other people with mild illness who are not at high risk of flu complications may also be treated early with antiviral drugs by their doctor, most people who are otherwise healthy and get flu do not need to be treated with antiviral drugs.

Generic Name: acyclovir (oral) (a SYE klo veer)
Brand Names: Sitavig, Zovirax

Medically reviewed by Sophia Entringer, PharmD Last updated on Jan 4, 2019.

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What is acyclovir?

Acyclovir is an antiviral drug. It slows the growth and spread of the herpes virus in the body. It will not cure herpes, but it can lessen the symptoms of the infection.

Acyclovir is used to treat infections caused by herpes viruses, such as genital herpes, cold sores, shingles, and chicken pox, as well as varicella (chickenpox), and cytomegalovirus.

Acyclovir may also be used for purposes not listed in this medication guide.

Take acyclovir for the entire length of time prescribed by your doctor. Your symptoms may get better before the infection is completely treated.

Treatment with acyclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

You should not take this medicine if you are allergic to acyclovir or valacyclovir (Valtrex). You should not take acyclovir buccal tablets (Sitavig) if you are allergic to milk proteins.

To make sure acyclovir is safe for you, tell your doctor if you have:

  • kidney disease; or

  • a weak immune system (caused by disease or by using certain medicine).

Acyclovir is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment.

Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

Acyclovir passes into breast milk, but is considered compatible with breast feeding. Tell your doctor if you are breast-feeding a baby while taking this medication.

Use in younger children is not recommended due to potential risk of choking.

How should I take acyclovir?

Take acyclovir exactly as it was prescribed for you. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

Treatment with acyclovir should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters).

Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.

To take the acyclovir buccal tablet (Sitavig):

  • Keep the tablet in its blister pack until you are ready to take it. Use a dry finger to remove the tablet.

  • Do not chew or swallow a buccal tablet. Place the flat side of the tablet against your upper gum, behind your lip and above your canine tooth. Place the tablet on the same side of the mouth as your cold sore.

  • Close your mouth and gently press on the outside of your lip over the tablet, holding it in place for 30 seconds. Avoid touching or pressing on the tablet once it is in place.

  • Allow the tablet to dissolve in your mouth throughout the day. You may eat and drink normally while the buccal tablet is in place.

  • During the first 6 hours of wearing time: If the tablet falls off or does not stick well, the same tablet should be repositioned immediately. If the tablet cannot be repositioned, a new tablet should be placed. If you accidentally swallow the tablet, drink a glass of water and put a new tablet in place.

Tell your doctor if you have any changes in weight. Acyclovir doses are based on weight (especially in children and teenagers), and any changes may affect the dose.

Drink plenty of water while you are taking acyclovir to keep your kidneys working properly.

Use this medicine for the full prescribed length of time. Your symptoms may improve before the infection is completely treated. Acyclovir will not treat a viral infection such as the flu or a common cold.

Lesions caused by herpes viruses should be kept as clean and dry as possible. Wearing loose clothing may help to prevent irritation of the lesions.

Store at room temperature away from moisture and heat.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

Overdose symptoms may include agitation, seizure (convulsions), or loss of consciousness.

What should I avoid while taking acyclovir?

Avoid brushing your teeth, chewing gum, or wearing an upper denture while you have a buccal tablet in your mouth. You may rinse your mouth gently. Drink plenty of liquids to prevent dry mouth.

Herpes infections are contagious and you can infect other people, even while you are being treated with acyclovir. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Taking this medicine will not prevent you from passing genital herpes to your sexual partner. Avoid sexual intercourse while you have active lesions or the first symptoms of an outbreak. Genital herpes may still be contagious through “viral shedding” from your skin, even if you have no symptoms.

Acyclovir side effects

Get emergency medical help if you have any signs of an allergic reaction to acyclovir: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • easy bruising or bleeding, purple or red pinpoint spots under your skin; or

  • signs of a kidney problem -little or no urinating; painful or difficult urination; swelling in your feet or ankles; feeling tired or short of breath.

Common acyclovir side effects may include:

  • nausea, vomiting;

  • diarrhea;

  • general ill feeling;

  • headache; or

  • mouth pain while using an acyclovir buccal tablet.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

More about acyclovir

  • Side Effects
  • During Pregnancy or Breastfeeding
  • Dosage Information
  • Patient Tips
  • Drug Images
  • Drug Interactions
  • Compare Alternatives
  • Support Group
  • Pricing & Coupons
  • 149 Reviews
  • Drug class: purine nucleosides
  • FDA Alerts (1)
  • Acyclovir Buccal Tablets
  • Acyclovir Capsules and Tablets
  • Acyclovir Injection
  • Acyclovir Suspension
  • Acyclovir Buccal mucosa (Advanced Reading)
  • Acyclovir Oral, Intravenous (Advanced Reading)

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