Acyclovir is the generic name for Zovirax, a prescription medication used to treat certain virus infections.
The Food and Drug Administration (FDA) approved acyclovir to treat viral infections from the varicella virus that causes chicken pox and shingles, as well as infections from the virus that causes genital herpes.
Sometimes doctors prescribe acyclovir to treat herpes infections in people with HIV.
The drug works by preventing viruses from dividing and multiplying. The FDA approved acyclovir in the 1980s.
Acyclovir is available as a generic, made by several companies, or under the brand name Zovirax, made by GlaxoSmithKline and available in tablet, capsule, and liquid form.
Acyclovir is one of the oldest drugs used to treat herpes simplex viruses and remains the first line of treatment for these infections.
However, research shows that acyclovir is not as effective as it used to be.
A 2013 study, published in the journal Current Opinion in Infectious Diseases, found that acyclovir-resistant herpes strains could develop over time.
Resistance happens in people with a healthy immune system as well as in those with a weakened immune system.
It's important to know that acyclovir does not cure viral infections. However, it can make infections shorter and less serious for some people.
If you're taking acyclovir for genital herpes, it can reduce the severity or prevent recurrences of a herpes outbreak.
If you're taking acyclovir to treat chicken pox or shingles, the drug can reduce the severity of your infection.
It's important to know that treatment with acyclovir works best when you start taking it as soon as possible after a rash appears.
This means within three days of a shingles rash and within 24 hours of a chicken pox rash.
It's usually not necessary to treat young, healthy children with chicken pox, but older children or adults who get chicken pox may need treatment.
Drink plenty of fluids when taking this medication. Children younger than 2 should not take acyclovir.
Use acyclovir with caution if you have kidney disease or any condition that weakness your immune system. If you have these conditions, you could be at risk for serious reactions to acyclovir.
Ask your doctor for advice on practicing safe sex if you have a genital herpes infection. Genital herpes spreads through sexual activity, and taking acyclovir alone may not be enough to prevent it.
If you're a woman, let your doctor know if you are or may be pregnant or if you're breastfeeding.
Researchers have not studied acyclovir use by pregnant women, so there's not enough evidence to say that it is safe to take during pregnancy.
Acyclovir also may pass into breast milk.
The most common side effects of acyclovir treatment for genital herpes include nausea, vomiting, and diarrhea.
Shingles requires treatment with higher doses of acyclovir, and the most common side effects at higher doses are tiredness and malaise.
Tell your doctor if you have any side effects. Side effects that may be seen in all people using acyclovir include:
Serious side effects also can occur. If you have any of these side effects, call your doctor right away:
Age matters, too. People older than 65 may have more side effects from acyclovir because their kidneys do not get rid of the drug as quickly as younger people's do.
Some drugs may affect the way acyclovir works, and acyclovir may affect other drugs you are taking.
It's very important to let your doctor know about all drugs you are taking, including any over-the-counter herbs or supplements.
Drugs that may interact with acyclovir include:
You do not need to change your diet or your activities while on acyclovir.
However, drink plenty of fluids when taking this medication.
Your dose of acyclovir will depend on why you're taking it.
Acyclovir comes in tablets, capsules, and liquid form. You can take it with or without food.
Lower doses may be best for elderly people and for anyone with kidney disease.
Common dosages are:
An overdose of acyclovir can cause kidney damage.
Symptoms of an overdose may include:
If you think that you or someone else has overdosed, call a poison control center at 1-800-222-1222.
If you or someone else has any severe symptoms after an overdose, call 9-1-1.
You should take acyclovir exactly as directed by your doctor. Also, do not stop taking acyclovir on your own.
Skipping doses or stopping too soon may not completely treat your infection, or it could make the infection harder to treat.
If you miss a dose of acyclovir, take the missed dose as soon as you remember.
If it's almost time for your next dose, skip the missed dose.
Do not double your dose to make up for a missed dose.
A: The most common adverse reactions associated with acyclovir (http://www.everydayhealth.com/drugs/zovirax) taken orally include malaise (generalized discomfort), headaches, nausea, vomiting and diarrhea. acyclovir used topically has the following as the most common adverse reactions: mild pain, burning or stinging and pruritus (itching). There have been rare (less than 1 percent of studied patients) that have had suspected effects on various organ systems such as liver, kidneys, heart, etc. As always, talk with your health care provider regarding questions you have about side effects of your prescription medications. Jen Marsico, RPh
A: Acyclovir (Zovirax) http://www.everydayhealth.com/drugs/acyclovir is a medication used to treat viral infections. The most common side effects associated with the oral form of Acyclovir are diarrhea, nausea, vomiting, headache, and feeling tired (malaise). Acyclovir cream and ointment can cause skin irritation. A search of the prescribing information for Acyclovir did not specifically list uncontrollable muscle twitching as a side effect. Tell your health-care provider about any negative side effects from prescription drugs. You can also report them to the U.S. Food and Drug Administration by visiting www.fda.gov/medwatch or by calling 1-800-FDA-1088. For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Lori Mendoza, PharmD
A: Acyclovir (Zovirax) is an antiviral medication indicated for the acute treatment of herpes zoster (shingles), the treatment of initial episodes and the management of recurrent episodes of genital herpes and the treatment of chickenpox. Acyclovir is only approved, by the U.S. Food and Drug Administration (FDA), for the treatment of chickenpox in the pediatric population 2 year of age and older. The safety and effectiveness of oral acyclovir in the pediatric population, younger than 2 years of age, has not been established. The dosage and administration of oral acyclovir depends upon the indication for use and age of the patient. Acyclovir can be administered with or without food. Acyclovir is the generic equivalent of Zovirax and is currently available, for oral administration, in capsule and tablet form and as a suspension for patients who have difficulty swallowing pills. Treatment with acyclovir should be initiated as soon as possible after the first appearance of symptoms, such as tingling, burning or blisters. Patients being treated with acyclovir are advised to stay adequately hydrated and take each dose with a full glass of water to protect the kidneys. The most frequently reported adverse reactions differed among clinical trials of acyclovir depending on the indication for use. During clinical trials of treatment with acyclovir, the most frequently reported adverse reactions included nausea, vomiting, diarrhea, malaise and headache. For the treatment of shingles, there is no information regarding initiation of treatment more than 72 hours following the onset of rash. Patients should initiate treatment as soon as possible after diagnosis. For the treatment of chickenpox, information gathered during clinical studies reflects initiation of treatment within 24 hours following rash. There is no information available regarding the effectiveness of treatment initiated after 24 hours. Patients should be advised that acyclovir is not a cure for genital herpes and there is no available research regarding whether acyclovir will prevent the transmission of the virus to other individuals.
A: The most frequently reported side effects of acyclovir (Zovirax), for oral administration, differed in clinical trials depending on the indication for use. During clinical trials of treatment of genital herpes, with short-term administration of acyclovir, the most frequently reported adverse reactions included nausea and/or vomiting. During clinical trials of treatment with long-term administration with acyclovir for genital herpes, there were two methods of administration evaluated. In trials evaluating continuous administration to prevent recurrences, the most frequently reported adverse reactions included nausea and diarrhea and in those evaluating intermittent treatment of recurrences over one year diarrhea, nausea and headache were reported. The most frequently reported adverse reaction during clinical trials of shingles was malaise. Lastly, during clinical trials of treatment of chickenpox with acyclovir, the most frequently reported adverse reaction was diarrhea. More serious side effects of acyclovir are possible with treatment. Kidney failure, in some cases causing death, has been reported with acyclovir treatment. Patients are advised to maintain adequate hydration and drink plenty of water while taking acyclovir to keep the kidneys working properly. There is also a warning regarding thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which has occurred in immunocompromised patients administered acyclovir. Patients should be advised to contact their health care provider immediately if they experience symptoms which may indicate the occurrence of more serious side effects of acyclovir. Symptoms may include pain the lower back, urinating less than usual or not urinating at all, easy bruising or bleeding, and unusual weakness. Patients are instructed to consult with their health care provider if they experience any other unusual, severe or troublesome side effects while being treated with acyclovir.
A: There is an acyclovir (Zovirax) ointment formulation, available in 5% strength. Currently, acyclovir ointment is only available as the brand-name Zovirax Ointment 5%. Acyclovir ointment is indicated for the management of initial genital herpes and in limited non-life threatening mucocutaneous herpes simplex virus infections in immunocompromised patients. Acyclovir ointment is not indicated for the prevention of viral transmission to other individuals. Acyclovir ointment is also not indicated for the prevention of recurrent herpes infections. Acyclovir ointment is a prescription ointment that is applied directly to genital herpes lesions and may lessen the duration of the symptoms associated with an initial outbreak. For the management of genital herpes, patients should be instructed regarding appropriate dosage and administration of acyclovir ointment. Patients should be advised to apply a sufficient quantity of acyclovir ointment to adequately cover all lesions and apply every 3 hours, 6 times daily, for 7 days of treatment. The dose size of acyclovir ointment for each application may vary depending on the size of the lesion area. However, the dose size should be approximately Â½ inch ribbon of acyclovir ointment per 4 square inches of surface area, according to the prescribing information. Patients should be advised to wear a rubber glove or finger cot when applying acyclovir ointment to the affected area to avoid spreading the virus. Acyclovir ointment should be applied as early as possible after the development of signs and symptoms. During controlled clinical trials, mild pain, including temporary burning and stinging, was reported in approximately 30% of patients with no significant difference between patients receiving Zovirax ointment and patients receiving placebo. Local pruritus was also reported in 4% of patients. Acyclovir ointment 5% should be used exactly as prescribed by a health care provider. Patients should be advised not to exceed the recommended dosage, frequency of applications and length of treatment.
A: How long acyclovir (Zovirax) treatment is intended for depends upon the indication for use. Acyclovir is a prescription antiviral agent approved, by the U.S. Food and Drug Administration (FDA), for the acute treatment of herpes zoster (shingles), the treatment of initial episodes and the management of recurrent episodes of genital herpes and the treatment of chickenpox. Acyclovir treatment is approved for all indications for adults and for the treatment of chickenpox in children 2 year of age and older. For the acute treatment of shingles, the length of acyclovir treatment is 7 to 10 days. The usual recommended adult dosage is 800 mg administered every 4 hours, 5 times daily. For the treatment of initial episodes of genital herpes, the length of acyclovir treatment is 10 days. The usual recommended adult dosage is 200 mg administered every 4 hours, 5 times daily. For the management of recurrent episodes of genital herpes, there were two methods of administration of acyclovir treatment evaluated in clinical trials. For intermittent therapy, the length of acyclovir treatment is 5 days. Treatment should be initiated at the earliest sign or symptom of recurrence, known as a prodrome. The usual adult dosage is 200 mg administered every 4 hours, 5 times daily. The other option is chronic suppressive therapy in which acyclovir treatment is used for up to 12 months and followed by re-evaluation by a health care provider to assess the need for continued treatment. The usual adult dosage is 400 mg twice daily. Alternative dosages may range from 200 mg 3 times daily to 200 mg 5 times daily, according to the prescribing information for Zovirax, the brand-name of acyclovir. For the treatment of chickenpox for adults and children, the recommended length of acyclovir treatment is 5 days. When treatment is required, it should be initiated at the earliest sign or symptom of chickenpox. The effectiveness of treatment initiated after 24 hours following the onset of symptoms is unknown. The usual dosage for adults and children weighing over 40 kg is 800 mg administered 4 times daily. The usual dosage for children 2 years of age and older is 20 mg/kg per dose administered 4 times daily.
A: During post marketing experience, observed in clinical practice, acyclovir (Zovirax) was reported to cause hair loss. However, because adverse reactions reported in clinical practice, and not during controlled clinical trials, are reported voluntarily from an unknown population size, the frequency of the adverse reaction is unknown. Other adverse reactions reported during post marketing experience with acyclovir included headache, allergic reaction, fever, pain, swelling in the extremities, agitation, confusion, dizziness, somnolence, tremors, diarrhea, gastrointestinal distress, nausea, anemia, leucopenia, thrombocytopenia, elevated liver enzymes, hepatitis, jaundice, myalgia, prutitus, rash, visual disturbances, kidney failure, kidney pain, elevated blood urea nitrogen (BUN) and creatinine, and hematuria. According to the prescribing information for Zovirax, the brand-name of acyclovir, the most frequently reported adverse reactions reported during clinical trials included nausea, vomiting, diarrhea, malaise and headache and varied depending on the indication for treatment. Patients are instructed to contact their health care provider, immediately, if they experience symptoms which may indicate more serious adverse reactions of acyclovir have developed. Symptoms may include pain the lower back, urinating less than usual or not urinating at all, easy bruising or bleeding, and unusual weakness. It is important for patients to report any unusual or bothersome reactions they experience while being treated with acyclovir. Acyclovir should be taken exactly as prescribed.
A: There are not many acyclovir (Zovirax) interactions with other medications. If acyclovir interacts with certain other medications, the effects can be increased, decreased or altered. One acyclovir interaction possible is with the medication probenecid (Benemid). It is especially important for patients taking probenecid to consult with a health care provider prior to treatment with acyclovir. If you are currently taking probenecid, you may not be able to take acyclovir, or you may require dosage adjustments of special tests during treatment. Some of the other possible acyclovir interactions with other medications may include Demerol (meperidine), Dilantin (phenytoin), Cellcept (mycophenolate mofetil), Viread (tenofovir), Zanaflex (tizanidine), Depakene (valproic acid), Retrovir (zidovudine), theophyllines and the varicella virus vaccine. It is essential for patients to consult with their health care provider regarding all prescription and over the counter medications they take prior to initiation of treatment with acyclovir to avoid potentially dangerous drug interactions. This includes all vitamins, minerals, herbal supplements and any drugs prescribed by another doctor.
A: During clinical trials, patients did not report acyclovir (Zovirax) causing stomach pain. However, most of the frequently reported adverse reactions associated with acyclovir treatment were related to the gastrointestinal system. According to the prescribing information for Zovirax, the brand-name equivalent of acyclovir, the most frequently reported gastrointestinal adverse reactions reported by patients during clinical trials for any indication included nausea, vomiting and diarrhea. In addition, post marketing experience revealed other gastrointestinal related adverse reactions observed in clinical practice. In clinical practice experience with acyclovir, patients reported experiencing diarrhea, gastrointestinal distress and nausea. There was no further description regarding gastrointestinal distress and whether or not patients experienced stomach pain specifically. Other common adverse reactions possible with acyclovir treatment include headache and malaise. It is essential for patients to consult a health care provider if they experience any unusual or bothersome adverse reactions while being treated with acyclovir for further evaluation. Acyclovir is an antiviral medication available by prescription only. Acyclovir is indicated for the acute treatment of shingles, the treatment of initial episodes and the management of recurrent episodes of genital herpes and the treatment of chickenpox. Acyclovir is approved for use in adults for all indications and for the treatment of chickenpox in the pediatric population in children 2 years of age and older. Acyclovir may be taken without regard to food and should be taken exactly as instructed by a health care provider.
A: Shingles is a painful rash that is caused by the same virus (varicella virus) that causes the chickenpox. Only people who were infected with the virus and got chickenpox can get shingles. Unfortunately, people with weakened immune systems, from other diseases like cancer or treatments like chemotherapy, are at much greater risk of developing shingles. Drugs like acyclovir (Zovirax) work to reduce the ability of the virus to multiply and spread in the body. Acyclovir has been shown to reduce the duration of infection and the severity of symptoms, but it relies on an individual's immune system to attack the virus. The drug itself does not kill the virus and that is likely the reason you continue to have symptoms and relapses. It is possible that some of the painful effects you are experiencing are the result of complications of shingles. One of these complications is called postherpetic neuralgia, which is the painful, tingling, and stinging pain at the site of the initial rash. There are medications that are used to help treat the pain associated with the nerve damage of shingles. These drugs include the anticonvulsants, such as Neurontin (gabapentin), Lyrica (pregabalin), and Tegretol (carbamazepine) and tricyclic antidepressants like Elavil (amitriptyline). For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Michelle McDermott, PharmD
A: Acyclovir (Zovirax) is used to decrease pain and speed the healing of sores or blisters in people who have varicella (chickenpox), herpes zoster (shingles; a rash that can occur in people who have had chickenpox in the past), and first-time or repeat outbreaks of genital herpes (a herpes virus infection that causes sores to form around the genitals and rectum from time to time). Acyclovir is also sometimes used to prevent outbreaks of genital herpes in people who are infected with the virus. Acyclovir is in a class of antiviral medications called synthetic nucleoside analogues. Dosage adjustment is recommended when administering acyclovir to patients with renal impairment. For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Shereen Gharbia, PharmD
A: Acyclovir (Zovirax) is an antiviral medication that can be used in the treatment of the herpes virus, including genital herpes, cold sores, and shingles. Acyclovir can also be used to help with the chicken pox virus. The most frequently reported adverse reactions differed among clinical trials of acyclovir depending on the indication for use. During clinical trials of treatment with acyclovir, the most frequently reported adverse reactions included nausea, vomiting, diarrhea, malaise and headache. For more specific information, consult with your doctor or pharmacist for guidance based on your health status and current medications, particularly before taking any action. Kristen Dore, PharmD
By Chris Iliades, MD, and Mary Elizabeth Dallas | Medically Reviewed by Niya Jones, MD, MPH
Latest Update: 2014-05-22
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