When This Medicine Should Not Be Used:
You should not use this medicine if you have had an allergic reaction to acyclovir or to similar medicines such as famciclovir (Famvir®), ganciclovir (Cytovene®, Vitrasert®), valacyclovir (Valtrex®), or valganciclovir (Valcyte™).

How to Use This Medicine:
Capsule, Tablet, Liquid

• Your doctor will tell you how much medicine to use. Do not use more than directed.
• Take this medicine at the first sign of a herpes breakout, or as soon as possible after you are diagnosed with herpes zoster. The medicine may not work if you wait longer than 3 days to start using it.
• You may take this medicine with or without food.
• Drink extra fluids so you will urinate more often and help prevent kidney problems.
• Shake the oral liquid thoroughly before each use. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.

Drugs and Foods to Avoid:
Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

• Tell your doctor if you are receiving any medicines that weaken the immune system (such as steroids, chemotherapy, or radiation).

Warnings While Using This Medicine:

• Make sure your doctor knows if you are pregnant or breast feeding. Tell your doctor if you have kidney disease or a weak immune system. Some things that cause a weak immune system are cancer chemotherapy, HIV/AIDS, recent infection, or recent bone marrow or kidney transplant.
• Acyclovir will not stop the spread of herpes during sex. Avoid having sex while you have herpes sores.
• Even if you have no signs of a herpes infection, it is still possible to spread the virus to others during sex. Talk with your doctor about ways to keep from spreading the virus.
• Call your doctor if your symptoms do not improve or if they get worse.

Possible Side Effects While Using This Medicine:
Call your doctor right away if you notice any of these side effects:

• Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
• Blistering, peeling, red skin rash.
• Confusion, agitation, behavior changes.
• Decrease in how much or how often you urinate.
• Fainting or extreme weakness, problems with walking or coordination.
• Pinpoint red spots on your skin.
• Unexplained fever.
• Unusual bleeding or bruising, blood in your urine or stools.
• Yellowing of your skin or the whites of your eyes.

If you notice these less serious side effects, talk with your doctor:

• Headache, muscle pain.
• Nausea, vomiting, diarrhea, or upset stomach.
• Nervousness or tired feeling.
• Problems with vision.

If you notice other side effects that you think are caused by this medicine, tell your doctor.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088