Acyclovir injection is used to treat first-time or repeat outbreaks of herpes simplex (a herpes virus infection of the skin and mucus membranes) and to treat herpes zoster (shingles; a rash that can occur in people who have had chickenpox in the past) in people with weak immune systems. It is also used to treat first-time genital herpes outbreaks (a herpes virus infection that causes sores to form around the genitals and rectum from time to time) in people with normal immune systems. Acyclovir injection is used to treat herpes simplex encephalitis (brain infection with swelling caused by the herpes virus) and herpes infections in newborn infants. Acyclovir injection 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 injection will not cure genital herpes and may not stop the spread of genital herpes to other people.

Acyclovir injection comes as a solution to be injected intravenously (into a vein). It is usually given over 1 hour every 8 hours. The length of treatment depends on your general health, the type of infection you have, your age, and how well you respond to the medication. Your doctor will tell you how long to use acyclovir injection.

You may receive acyclovir injection in a hospital or you may administer the medication at home. If you will be receiving acyclovir injection at home, your healthcare provider will show you how to use the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions.

Before using acyclovir injection,

• tell your doctor and pharmacist if you are allergic to acyclovir, valacyclovir (Valtrex), any other medications, or any of the ingredients in acyclovir injection. Ask your pharmacist for a list of the ingredients.
• tell your doctor and pharmacist what other 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: probenecid (Benemid, in Colbenemid). Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
• tell your doctor if you have or have ever had problems with your immune system, human immunodeficiency virus infection (HIV), or acquired immunodeficiency syndrome (AIDS); or kidney or liver disease. Also tell your doctor if there is a possibility you may be dehydrated from a recent illness or activity.
• tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while receiving acyclovir injection, call your doctor.

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
• coma
• seizures
• tiredness

Unless your doctor tells you otherwise, continue your normal diet.

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

• redness or swelling at the injection site
• nausea
• vomiting

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

• rash
• hives
• itching
• difficulty breathing or swallowing
• swelling of the face, throat, tongue, lips, eyes
• hoarseness

Acyclovir injection may cause other side effects. Call your doctor if you have any unusual problems while receiving 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).

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

Keep all appointments with your doctor. Your doctor may order certain lab tests to check your body's response to acyclovir injection.

Do not let anyone else take 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.