Acyclovir Side Effects

by on January 16, 2012

Side effects associated with Acyclovir (Zovirax) occur rarely and when they do, they are usually very mild.  The most commonly experienced side effects include diarrhea, nausea and general malaise. More serious side effects of acyclovir,  such as unusual bleeding or bruising, seizures, changes in mood and behavior or problems with vision, could indicate a more serious condition and should be reported to a doctor immediately.

Common Acyclovir Side Effects

The side effects of Acyclovir experienced by most patients are mild and very manageable. They include the following:

  • Nausea
  • Vomiting
  • Headaches
  • Diarrhea
  • Generalized feeling of illness, or malaise

The underlying infection that is being treated may have an impact on which Acyclovir side effects you experience. Nausea was most common in patients being treated for genital herpes. Chickenpox patients experienced diarrhea most often as one of the Acyclovir side effects.

Those who were taking acyclovir medication for herpes zoster experienced malaise as the most common side effect.

If any of the above side effects persist, worsen or have a significant impact on your daily activities, you should consult your doctor.

Serious Acyclovir Side Effects

Some patients find that they are allergic to acyclovir medications. In the event of an allergic reaction, it is important to contact your healthcare provider immediately. Side effects associated with an allergic reaction include the following:

  • Rash or hives
  • Itching
  • Swelling of the face or throat
  • Tightness of the chest
  • Difficulty breathing

Other serious acyclovir side effects may include:

  • Change in the amount of urine produced
  • Changes in mood or thoughts such as aggressiveness
  • Hallucinations
  • Unsteady or shaky movements
  • Insomnia
  • Unusual bleeding or bruising

If you experience any of the above, you should contact your doctor immediately.  Side effects such as changes in moods or thoughts can be difficult to identify, so be sure to let you doctor know if you have a general feeling that things are not quite right while using this medication.


Very rarely, side effects may indicate a dangerous disorder of the kidneys and blood cells. This is known as thrombotic thrombocytopenic purpura / hemolytic uremic syndrome (TTP/HUS). This condition causes the body to form several small blood clots. If you experience any of the following symptoms, you may be dealing with this life-threatening condition. Contact your healthcare provider immediately.

  • Fever
  • Dark or bloody urine
  • Severe abdominal pain
  • Yellowing of the eyes or skin
  • Changes in vision
  • Seizures
  • Extreme fatigue
  • Easy bleeding or bruising
  • Rapid, slow or irregular heartbeat

Acyclovir and the Kidneys

One of the potential Acyclovir side effects is kidney damage. If you already have kidney disease, you are at a higher risk of experiencing this side effect. Talk to your doctor about your condition before you begin taking acyclovir medications. You may still be able to use acyclovir, but you will likely need a lower dosage and careful monitoring for signs of kidney damage.

Acyclovir is an effective treatment option for patients struggling with the pain, discomfort and appearance of herpes outbreaks. Remember that this medication will not cure you of the herpes virus. You may still be able to spread genital herpes throughout the outbreak, so you should continue to take the appropriate precautions. As side effects with acyclovir medications are typically mild, most patients will find this to be a useful treatment for limiting the length and severity of outbreaks.