- 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 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).
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
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...
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...
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?...
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 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 Herpes Zoster
Also called shingles, zona, and zoster. The culprit is the varicella-zoster virus. Primary infection with this virus causes...
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 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 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 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
Shingles, or herpes zoster, is a painful rash caused by the varicella zoster virus. Other shingles symptoms include headache,...
STDs in Men
Sexually transmitted diseases (STDs) are infections transmitted during sexual contact. They may be caused by viruses, bacteria,...
There are a variety of diseases and conditions that can cause tongue problems, discoloration, and soreness. Though most tongue...
Pityriasis rosea is a rash that begins with a large pink patch with well-defined scaly borders on the back, chest, or neck. In...
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...
Sexually Transmitted Diseases in Women (STD)
Sexually transmitted diseases (STDs) are among the most common infectious diseases in the United States. STDs can be spread...
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...
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"...
Chickenpox (chicken pox) is a contagious childhood disease caused by the varicella-zoster virus. Symptoms have an incubation...
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...
Shingles and Pregnancy
Becoming infected with chickenpox during pregnancy could cause birth defects in your unborn child. Likewise, shingles could also...
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...
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...
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
- Drugs: Buying Prescription Drugs Online Safely
- Drugs: The Most Common Medication Errors
- 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
- Medication Disposal
- Dangers of Mixing Medications
- Home Remedies for Shingles
- What Are the Facts on Chicken Pox?
- Generic Drugs, Are They as Good as Brand-Names?
Medications & Supplements
Prevention & Wellness
Health Solutions From Our Sponsors
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.