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Acyclovir

(ay sye' kloe veer)

Brand Name(s): Sitavig®, Zovirax® Capsules, Zovirax® Tablets; also available generically

Other Name(s): Acycloguanosine, ACV

WHY is this medicine prescribed?

Acyclovir 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. It works by stopping the spread of the herpes virus in the body. Acyclovir will not cure genital herpes and may not stop the spread of genital herpes to other people.

Are there OTHER USES for this medicine?

Acyclovir is also sometimes used to treat eczema herpeticum (a skin infection caused by the herpes virus) to treat and prevent herpes infections of the skin, eyes, nose, and mouth in patients with human immunodeficiency virus (HIV), and to treat oral hairy leukoplakia (condition that causes hairy white or gray-colored patches on the tongue or inside of the cheek).

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

HOW should this medicine be used?

Acyclovir comes as a tablet, a capsule, and a suspension (liquid) to take by mouth. It also comes as a delayed-release buccal tablet to apply to the upper gum of the mouth. The tablets, capsules, and suspension are usually taken with or without food two to five times a day for 5 to 10 days, starting as soon as possible after your symptoms begin. When acyclovir is used to prevent outbreaks of genital herpes, it is usually taken two to five times a day for up to 12 months. The delayed-release buccal tablet is usually applied with a dry finger as a one-time dose within 1 hour after itching, redness, burning or tingling cold sore symptoms begin but before the cold sore appears. Take or use acyclovir at around the same time(s) every day. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take or use acyclovir exactly as directed. Do not take or use more or less of it or take it more often or for a longer time than prescribed by your doctor.

Do not chew, crush, suck, or swallow the delayed-release buccal tablets. Drink plenty of liquids, if you have a dry mouth while using the delayed-release buccal tablets.

To use buccal acyclovir, follow these steps:

  1. Find the area on the upper gum above your left and right incisor teeth (the teeth just to the left and right of your two front teeth).
  2. With dry hands, remove one delayed-release tablet from the container.
  3. Gently apply the tablet to the upper gum area as high as it will go on your gum above one of your incisor teeth on the side of your mouth with the cold sore. Do not apply it to the inside of the lip or cheek.
  4. Hold the tablet in place for 30 seconds.
  5. If the tablet does not stick to your gum or if it sticks to your cheek or the inside of your lip, reposition it to stick to your gum. Leave the tablet in place until it dissolves.
  6. Do not interfere with the placement of the tablet. Check to see if the tablet is still in place after eating, drinking, or rinsing your mouth.

If the delayed-release buccal tablet comes off within the first 6 hours of application, reapply the same tablet. If it still will not stick, then apply a new tablet. If you accidentally swallow the tablet within the first 6 hours of application, drink a glass of water and place a new tablet on your gum. If the tablet falls off or is swallowed 6 or more hours after application, do not apply a new tablet until your next regular time.

Avoid the following while you are using acyclovir buccal delayed-release tablet:

  • Do not chew gum, touch, or press the buccal tablet after it has been applied.
  • Do not wear upper dentures.
  • Do not brush your teeth until it dissolves. If your teeth need to be cleaned while the tablet is in place, rinse the mouth gently.

Shake the suspension well before each use to mix the medication evenly.

Your symptoms should improve during your treatment with acyclovir. Call your doctor if your symptoms do not improve or if they get worse.

Take or use acyclovir until you finish the prescription, even if you feel better. If you stop taking acyclovir too soon or skip doses, your infection may not be completely treated or may become more difficult to treat. The delayed-release buccal tablet is applied as a one-time dose.

What SPECIAL PRECAUTIONS should I follow?

Before taking acyclovir,

  • tell your doctor and pharmacist if you are allergic to acyclovir, valacyclovir (Valtrex), any other medications, milk proteins, or any of the ingredients in acyclovir products. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention any of the following: amphotericin B (Fungizone); aminoglycoside antibiotics such as amikacin (Amikin), gentamicin (Garamycin), kanamycin (Kantrex), neomycin (Nes-RX, Neo-Fradin), paramomycin (Humatin), streptomycin, and tobramycin (Tobi, Nebcin); aspirin and other nonsteroidal anti-inflammatory drugs such as ibuprofen (Advil, Motrin), and naproxen (Aleve, Naprosyn); cyclosporine (Gengraf, Neoral, Sandimmune); medications to treat HIV or AIDS such as zidovudine (Retrovir, AZT); pentamidine (NebuPent); probenecid (Benemid); sulfonamides such as sulfamethoxazole and trimethoprim (Bactrim); tacrolimus (Prograf); and vancomycin. Many other medications may also interact with acyclovir, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if there is a possibility you may be dehydrated from a recent illness or activity, or if you have or have ever had problems with your immune system; human immunodeficiency virus infection (HIV); acquired immunodeficiency syndrome (AIDS); or kidney disease.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while taking acyclovir, call your doctor.
  • if you are taking acyclovir to treat genital herpes, you should know that genital herpes can be spread through sexual contact even if you don't have blisters or other symptoms and possibly even if you are taking acyclovir. Talk to your doctor about ways to stop the spread of genital herpes and about whether your partner(s) should receive treatment.

What SPECIAL DIETARY instructions should I follow?

Drink plenty of fluids while you are taking or using acyclovir.

What should I do IF I FORGET to take a dose?

Take the missed dose as soon as you remember it and take any remaining doses for that day at evenly spaced intervals. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

What SIDE EFFECTS can this medicine cause?

Acyclovir may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • upset stomach
  • vomiting
  • diarrhea
  • dizziness
  • tiredness
  • agitation
  • pain, especially in the joints
  • hair loss
  • changes in vision

Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately:

  • hives
  • rash or blisters
  • itching
  • difficulty breathing or swallowing
  • swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
  • hoarseness
  • fast heartbeat
  • weakness
  • pale skin
  • difficulty sleeping
  • fever, sore throat, chills, cough, and other signs of infection
  • unusual bruising or bleeding
  • blood in the urine
  • stomach pain or cramps
  • bloody diarrhea
  • decreased urination
  • headache
  • hallucinations (seeing things or hearing voices that do not exist)
  • confusion
  • aggressive behavior
  • difficulty speaking
  • numbness, burning, or tingling in the arms or legs
  • temporary inability to move parts of your body
  • shaking of a part of your body that you cannot control
  • seizures
  • loss of consciousness

Acyclovir may cause other side effects. Call your doctor if you have any unusual problems while you are taking or using this medication.

If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088).

What should I know about STORAGE and DISPOSAL of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach. http://www.upandaway.org

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA's Safe Disposal of Medicines website (http://goo.gl/c4Rm4p) for more information if you do not have access to a take-back program.

What should I do in case of OVERDOSE?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at https://www.poisonhelp.org/help. If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

Symptoms of overdose may include the following:

  • agitation
  • seizures
  • extreme tiredness
  • loss of consciousness
  • swelling of the hands, feet, ankles, or lower legs
  • decreased urination

What OTHER INFORMATION should I know?

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your response to acyclovir.

Do not let anyone else take or use your medication. Ask your pharmacist any questions you have about refilling your prescription.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


This report on medications is for your information only, and is not considered individual patient advice. Because of the changing nature of drug information, please consult your physician or pharmacist about specific clinical use.

The American Society of Health-System Pharmacists® represents that the information provided hereunder was formulated with a reasonable standard of care, and in conformity with professional standards in the field. The American Society of Health-System Pharmacists® makes no representations or warranties, express or implied, including, but not limited to, any implied warranty of merchantability and/or fitness for a particular purpose, with respect to such information and specifically disclaims all such warranties. Users are advised that decisions regarding drug therapy are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and the information is provided for informational purposes only. The entire monograph for a drug should be reviewed for a thorough understanding of the drug's actions, uses and side effects. The American Society of Health-System Pharmacists® does not endorse or recommend the use of any drug. The information is not a substitute for medical care.

Pronunciation Guide for Drug Names is used with permission. © 2009. The United States Pharmacopeial Convention. All Rights Reserved.

AHFS® Patient Medication Information™. © Copyright, 2020. The American Society of Health-System Pharmacists®, 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

Selected Revisions: November 15, 2019.