What side effects can this medication 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 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 at http://www.fda.gov/MedWatch/report.htm or by phone 1-800-332-1088.