Acyclovir is an antiviral drug. Acyclovir is used to treat infections caused by certain types of viruses. However, it is not a cure for these infections. The viruses that cause these infections continue to live in the body even between outbreaks. Acyclovir decreases the severity and length of these outbreaks. It helps the sores heal faster, keeps new sores from forming, and decreases pain/itching.

• It treats cold sores around the mouth (caused by herpes simplex), shingles (caused by herpes zoster), and chickenpox.
• This medication is also used to treat outbreaks of genital herpes.
• In people with frequent outbreaks, acyclovir is used to help reduce the number of future episodes.
• This medication may also help reduce how long pain remains after the sores heal.
• In addition, in people with a weakened immune system, acyclovir can decrease the risk of the virus spreading to other parts of the body and causing serious infections.

Some of the more common side effects of acyclovir oral tablet include:

• Nausea
• Vomiting
• Diarrhea
• Headache
• Weakness

Serious side effects

Call your doctor right away if you have serious side effects. Serious side effects and their symptoms can include the following:

Unusual changes in your mood or behavior. Symptoms can include:

• aggressive behavior

• unsteady or shaky movements

• confusion

• trouble speaking

• hallucinations (seeing or hearing something that isn’t there)

• seizures

• coma (being unconscious for a long time)

Decrease in your red blood cells and platelets. Symptoms can include:

• fatigue

• Liver problems

• Muscle pain

Skin reactions. Symptoms can include:

• hair loss
• rash
• breaking or loosening of skin
• hives
• Stevens-Johnson syndrome. This is a rare, allergic skin reaction.
• Changes in your vision

• Kidney failure. Symptoms can include:

  • kidney or flank pain (pain in your side and back)

  • blood in your urine

Allergic reaction. Symptoms can include:

• trouble breathing

• swelling of your throat or tongue

• rash

• hives

• If your symptoms do not improve within a few days, or if they become worse, check with your doctor.
• The areas affected by herpes, chickenpox, or shingles should be kept as clean and dry as possible. Also, wear loose-fitting clothing to avoid irritating the sores (blisters).
• It is important to remember that acyclovir will not keep you from spreading herpes to others.
• Herpes infection of the genitals can be caught from or spread to your partner during any sexual activity. Even though you may get herpes if your partner has no symptoms, the infection is more likely to be spread if sores are present. This is true until the sores are completely healed and the scabs have fallen off. Therefore, it is best to avoid any sexual activity if either you or your sexual partner has any symptoms of herpes. The use of a latex condom (“rubber”') may help prevent the spread of herpes. However, spermicidal (sperm-killing) jelly or a diaphragm will probably not help.