- Sexually Transmitted Diseases (STDs) Slideshow Pictures
- Image Collection: Picture of Genital Warts (HPV)
- Take the Genital Herpes Quiz
- What is acyclovir, and how does it work (mechanism of action)?
- What brand names are available for acyclovir?
- Is acyclovir available as a generic drug?
- Do I need a prescription for acyclovir?
- What are the side effects of acyclovir?
- What is the dosage for acyclovir?
- Which drugs or supplements interact with acyclovir?
- Is acyclovir safe to take if I'm pregnant or breastfeeding?
- What else should I know about acyclovir?
What is acyclovir, and how does it work (mechanism of action)?
Acyclovir is an antiviral drug, a synthetic nucleoside analogue, that has inhibitory activity (interferes with viral replication) against the herpes viruses, including herpes simplex 1 and 2 (cold sores and genital herpes), varicella-zoster (shingles and chickenpox), and Epstein-Barr virus (mononucleosis). Viruses take over living cells and reproduce themselves, often at the expense of the host cell. The acyclovir is converted to an active form by the virus itself, and the virus then uses the active form of acyclovir rather than the nucleoside it normally uses to manufacture DNA, a critical component of viral replication. Incorporation of active acyclovir into new viral DNA stops the production of the DNA. Virally infected cells absorb more acyclovir than normal cells and convert more of it to the active form, which prolongs its antiviral activity. The FDA approved acyclovir in March 1982.
What are the side effects of acyclovir?
The most common side effects are
Other reported side effects include:
What is the dosage for acyclovir?
Acyclovir may be taken with or without food.
- Adult oral doses for treating genital herpes are 200 mg every 4 hours (5 times daily) for 7-10 days or 400 mg three times daily for 5-10 days.
- Herpes Zoster (shingles) is treated with 800 mg every 4 hours (5 times daily) for 7 to 10 days.
- The dose for treating chicken pox is 800 mg 4 times daily. The usual adult intravenous dose is 5-10 mg/kg every 8 hours for 7-10 days.
Which drugs or supplements interact with acyclovir?
Acyclovir may decrease levels of phenytoin (Dilantin) or valproic acid (Depakote, Depakote ER). Probenecid (Benemid) may increase acyclovir serum levels by decreasing renal excretion of acyclovir. Acyclovir may increase serum levels of theophylline (Theo-Dur, Respbid, Slo-Bid, Theo-24, Theolair, Uniphyl, Slo-Phyllin).
Is acyclovir safe to take if I'm pregnant or breastfeeding?
There are no adequate studies of acyclovir in pregnant women. In a patient registry of women who used acyclovir during the first trimester, the rate of birth defects was similar to the rate of birth defects in the general population.
Acyclovir is excreted in breast milk, and a significant amount may be transferred to the infant.
What else should I know about acyclovir?
What preparations of acyclovir are available?
- Capsules: 200 mg.
- Tablets: 400 and 800 mg.
- Suspension: 200 mg/5 ml.
- Injection: 50 mg/ml.
- Powder for injection: 500 and 1000 mg.
- Ointment: 5%.
How should I keep acyclovir stored?
Acyclovir should be stored at room temperature, between 15 C 25 C (59 F to 77 F).
Reference: FDA Prescribing Information
Acyclovir (Zovirax) is an antiviral drug prescribed to treat genital herpes, shingles, and chickenpox. Side effects drug interactions, dosing, storage, and pregnancy safety information should be reviewed prior to taking this medication.
Multimedia: Slideshows, Images & Quizzes
Cold Sores Causes, Remedies, & Diagnosis
How to get rid of cold sores? First learn about the herpes virus and how it causes cold sores. When are cold sores contagious?...
Genital Herpes Quiz: What is Genital Herpes?
What is genital herpes? Learn the causes, symptoms in men and women, and treatments for this common sexually transmitted skin...
Shingles Quiz: Symptoms, Vaccine & Pictures
Shingles falls within a well-known family of viruses that cause itching, burning, blisters, and pain. Take the Shingles Quiz to...
Chickenpox Quiz: Test Your Medical IQ
How is chickenpox related to shingles? Take the Chickenpox Quiz to assess your IQ of this itchy, blistering childhood skin...
Picture of Shingles
An acute infection caused by the herpes zoster virus, the same virus as causes chickenpox. See a picture of Shingles and learn...
Picture of Herpes Zoster
Also called shingles, zona, and zoster. The culprit is the varicella-zoster virus. Primary infection with this virus causes...
Picture of Herpes Simplex Virus Type 1
A herpes virus that causes cold sores and fever blisters in and around the mouth. See a picture of Herpes Simplex Virus Type 1...
Picture of Varicella-Zoster Virus Infection (Face)
Multiple, very pruritic, erythematous papules, vesicles (“dewdrops on a rose petal”), and crusted papules on erythematous,...
Picture of Varicella (Chickenpox) Virus
A highly infectious viral disease, known familiarly as chickenpox. See a picture of the Varicella (Chicken Pox) Virus and learn...
Picture of Varicella Chicken Pox
Varicella Chickenpox is caused by a virus of the herpes group. The disease is highly contagious and is spread by droplet or...
Picture of Fixed Drug Eruption
A large red-violet plaque on the arm of a child. See a picture of Fixed Drug Eruption and learn more about the health topic....
Picture of Herpetic Whitlow
Painful grouped red-blue vesicles on the middle finger of a child. See a picture of Herpetic Whitlow and learn more about the...
Picture of Varicella-Zoster Virus Infection on Chest Wall
Typical grouped vesicles and pustules with erythema and edema of three contiguous thoracic dermatomes on the posterior chest...
Picture of Varicella-Zoster Virus Infection Close-Up
Grouped and confluent vesicles surrounding erythema on the chest wall. See a Varicella-Zoster Virus Infection: Close-Up and learn...
Related Disease Conditions
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...
Shingles, or herpes zoster, is a painful rash caused by the varicella zoster virus. Other shingles symptoms include headache,...
Pityriasis rosea is a rash that begins with a large pink patch with well-defined scaly borders on the back, chest, or neck. In...
There are a variety of diseases and conditions that can cause tongue problems, discoloration, and soreness. Though most tongue...
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"...
Sexually Transmitted Diseases in Women (STD)
Sexually transmitted diseases, or STDs, are infections that are transmitted during any type of sexual exposure, including...
Chickenpox (chicken pox) is a contagious childhood disease caused by the varicella-zoster virus. Symptoms have an incubation...
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...
Bell's Palsy (Facial Nerve Problems) Paralysis Causes and Treatments
Bell's palsy is one type of facial nerve paralysis. The 7th cranial nerve controls the muscles of the face, and although...
Ramsay Hunt Syndrome
Ramsay Hunt syndrome is an infection of a facial nerve that causes a red painful rash with blisters and facial paralysis. Other...
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...
Shingles and Pregnancy
Becoming infected with chickenpox during pregnancy could cause birth defects in your unborn child. Likewise, shingles could also...
Sexually Transmitted Diseases and Pregnancy (STDs)
When you are pregnant, many sexually transmitted diseases (STDs) can be especially harmful to you and your baby. These STDs...
Treatment & Diagnosis
- Shingles (Herpes Zoster) FAQs
- Genital Herpes FAQs
- Chickenpox FAQs
- Home Remedies for Shingles
- Prescriptions: Complying with the Doctor's Orders
- How To Reduce Your Medication Costs
- Pharmacy Visit, How To Get The Most Out of Your Visit
- Indications for Drugs: Approved vs. Non-approved
- Generic Drugs, Are They as Good as Brand-Names?
- Drugs: Buying Prescription Drugs Online Safely
- Drugs: The Most Common Medication Errors
- Medication Disposal - What to Do with Old or Unusable Medication
- Dangers of Mixing Medications
Medications & Supplements
Prevention & Wellness
Daily Health News
Subscribe to MedicineNet's General Health Newsletter
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.
Top acyclovir Related ArticlesComplete List
Chickenpox (Varicella)Chickenpox (chicken pox) is a contagious childhood disease caused by the varicella-zoster virus. Symptoms have an incubation period of 14 to 16 days and include a couple days of mild fever, weakness, and red, raised rash that progresses to blisters that eventually burst and crust over. Complications include bacterial infection of the open sores, scarring, encephalitis, nerve palsies, and Reye's syndrome.
Chickenpox QuizHow is chickenpox related to shingles? Take the Chickenpox Quiz to assess your IQ of this itchy, blistering childhood skin disease.
Cold Sores SlideshowHow to get rid of cold sores? First learn about the herpes virus and how it causes cold sores. When are cold sores contagious? Get information on triggers that can cause a flare up in cold sore symptoms.
Facial Nerve Problems
Bell's palsy is one type of facial nerve paralysis. The 7th cranial nerve controls the muscles of the face, and although scientists do not know the exact cause of Bell's palsy, they think it may be due to nerve damage from an infection, for example, the flu, common cold viruses, and more serious infections like meningitis. The symptoms of Bell's palsy vary from person to person, but can include:
- Mild weakness to total paralysis
- Dry eye
- Dry mouth
- Eyelid drooping
- Mouth drooping
- Dry mouth
- Changes in taste
- Excessive tearing in one eye
National Institute of Neurological Disorders and Stroke (NINDS). "NINDS Bell's Palsy Information Page." Updated: Apr 16, 2015.
PubMed Health. "Bell's Palsy."
NIH. National Center for Advancing Translational Sciences. "Bell's Palsy."
Genital Herpes in Women OverviewGenital 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.
Genital Herpes QuizWhat is genital herpes? Learn the causes, symptoms in men and women, and treatments for this common sexually transmitted skin disease.
Herpes Simplex Infections (Non-Genital)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 Simplex Virus Type Picture 1A herpes virus that causes cold sores and fever blisters in and around the mouth. See a picture of Herpes Simplex Virus Type 1 and learn more about the health topic.
Pimple vs Cold SorePimples 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.
Pityriasis RoseaPityriasis rosea is a rash that begins with a large pink patch with well-defined scaly borders on the back, chest, or neck. In one to two weeks, the person will develop many smaller pink patches on his or her trunk, arms, and legs. Symptoms include mild itching and possible sore throat, fatigue, nausea, aching, and decreased appetite. Pityriasis rosea typically resolves on its own and symptoms and signs may be treated with topical steroid creams and oral antihistamines.
Ramsay Hunt SyndromeRamsay Hunt syndrome is an infection of a facial nerve that causes a red painful rash with blisters and facial paralysis. Other symptoms of Ramsay Hunt syndrome may include:
- ear pain,
- hearing loss,
- dizziness (or vertigo),
- dry eye,
- and changes in taste sensation.
- antiviral agents,
- steroids, and
- pain medications.
Sexually Transmitted Diseases (STDs In Women)
Sexually transmitted diseases, or STDs, are infections that are transmitted during any type of sexual exposure, including intercourse (vaginal or anal), oral sex, and the sharing of sexual devices, such as vibrators. Women can contract all of the STDs, but may have no symptoms, or have different symptoms than men do. Common STDs in women are:
- Zika virus
- Genital herpes
- Hepatitis B
- Hepatitis C
- Pubic lice
- Genital warts
Treatment for STDs depends upon the type.
Shingles (Herpes Zoster)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.
Take the Shingles QuizShingles falls within a well-known family of viruses that cause itching, burning, blisters, and pain. Take the Shingles Quiz to get the facts, causes, symptoms, and treatments for this itchy, painful condition.
Tongue ProblemsThere are a variety of diseases and conditions that can cause tongue problems, discoloration, and soreness. Though most tongue problems are not serious. Conditions such as leukoplakia, oral thrush, and oral lichen planus may cause a white tongue while Kawasaki syndrome, scarlet fever, and geographic tongue may cause the tongue to appear red. A black hairy tongue may be caused by overgrown papillae on the tongue. Canker sores, smoking, and trauma may cause soreness of the tongue.