Side effects

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

• headache
• upset stomach
• vomiting
• diarrhea
• loss of appetite
• dizziness
• hair loss
• muscle or joint pain
• vision problems

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

• rash or blisters
• itching
• hives
• difficulty breathing or swallowing
• swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
• extreme tiredness
• confusion
• hallucinations (seeing things or hearing voices that are not really there)
• agitation
• shaking of a part of your body that you cannot control
• seizures
• unusual bleeding or bruising
• difficulty speaking
• numbness or tingling in the hands, arms, feet, or legs
• temporary inability to move part of your body
• stomach pain or cramps
• bloody diarrhea
• bloody urine
• fever

Acyclovir may cause other side effects. Call your doctor if you have any unusual problems while 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 at http://www.fda.gov/MedWatch/report.htm or by phone 1-800-332-1088.