Risks and Side Effects of Acyclovir

Risks and Side Effects of Acyclovir

Acyclovir has 

Acyclovir has the following characteristics:
1. it is an acyclic purine nucleoside analogue and antiviral agent used to treat:
a. Herpes Simplex (HSV) 1, 2
b. Herpes Zoster HZV (Shingles) &Varicella Zoster (Chickenpox)
c. To Prevent future Herpes Infections
d. Cytomegalovirus (CMV)
e. Ebstein-Barr virus (EBV)

2. Typical doseage is 800mg 5x per day for Herpes Zoster affecting the eye.
Oral or Genital Herpes Simplex is treated at 200-800mg 3-5 x per day for 5-10 days.
Prevention/prophylactic dose is 400 mg, 2x/day depending on patient & condition: we try to taper down to even lower if possible for eye conditions. 
3. Side effects are uncommon but are listed below.
4. Acyclovir is excreted largely unchanged by the kidneys: kidney damage is rare but can happen in patients who have kidney disease and maybe even in patients who do not drink enough water or have another predisposing factor for kidney damage from this medicine. 
5. Acyclovir does not really cause liver damage & thus any jaundice (yellowing of skin & white part of eyes) most often is due to the main Herpes infection.  

Side Effects

List acyclovir side effects by likelihood and severity.

The following side effects are associated with acyclovir:

Common side effects of acyclovir:

  • Not Feeling WellLess Severe

Infrequent side effects of acyclovir:

  • DiarrheaLess Severe
  • DizzyLess Severe
  • DrowsinessLess Severe
  • Feel Like Throwing UpLess Severe
  • Feeling RestlessLess Severe
  • Hair LossLess Severe
  • Head PainLess Severe
  • Irritation of the Stomach or IntestinesLess Severe
  • Muscle PainLess Severe
  • Numbness and TinglingLess Severe
  • Stomach CrampsLess Severe
  • Throwing UpLess Severe

Rare side effects of acyclovir:

  • Abnormal Liver Function TestsSevere
  • Aggressive BehaviorSevere
  • AnemiaSevere
  • Any Disorder of the BrainSevere
  • Bloody UrineSevere
  • ComaSevere
  • ConfusedSevere
  • Decreased Blood PlateletsSevere
  • Decreased White Blood CellsSevere
  • DeliriumSevere
  • Difficulty SpeakingSevere
  • Erythema MultiformeSevere
  • FeverSevere
  • Fluid Retention in the Legs, Feet, Arms or HandsSevere
  • Giant HivesSevere
  • HallucinationSevere
  • HepatitisSevere
  • High Amount of Bilirubin in the BloodSevere
  • HivesSevere
  • ItchingSevere
  • Kidney FailureSevere
  • Life Threatening Allergic ReactionSevere
  • Mental Disorder with Loss of Normal Personality & RealitySevere
  • Problems with EyesightSevere
  • RashSevere
  • SeizuresSevere
  • Stevens-Johnson SyndromeSevere
  • Swollen Lymph NodesSevere
  • Toxic Epidermal NecrolysisSevere
  • Yellowing of Skin or Eyes from Liver ProblemsSevere
  • Involuntary QuiveringLess Severe
  • Kidney PainLess Severe
  • PainLess Severe
  • Sun-Sensitive SkinLess Severe
  • UncoordinatedLess Severe

1. Side Effects

Nauseadiarrheaheadache, or vomiting may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Tell your doctor immediately if any of these unlikely but serious side effects occur: dizziness, drowsiness, signs of kidney problems (such as a change in the amount of urine, unusual back/side pain), mental/mood changes (such as agitation, confusion, hallucinations), shaky/unsteady movement, trouble speaking.
This medication may rarely cause a life-threatening disorder that affects the blood cellskidneys, and other parts of the body. This disorder is more likely to occur if you have conditions related to a weakened immune system (such as HIV disease, bone marrow transplantkidney transplant). Seek immediate medical attention if any of these rare but serious side effects occur: extreme tiredness, slow/fast/irregular heartbeat, easy bruising/bleeding, new fever, bloody/dark urine, severe stomach/abdominal pain, yellowing eyes/skin, sudden vision changes, loss of consciousness, seizures.
A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
In Canada – Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.


Acyclovir is used to treat infections caused by certain types of viruses. 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.
Acyclovir is an antiviral drug. 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. 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.

How to use acyclovir

Take this medication by mouth with or without food, usually 2 to 5 times a day as directed by your doctor. Drink plenty of fluids while taking this medication unless your doctor directs you otherwise.
If you are using the liquid form of this medication, shake the bottle well before each dose. Carefully measure the dose using a special measuring device/spoon. Do not use a household spoon because you may not get the correct dose.
This medication works best when started at the first sign of an outbreak, as directed by your doctor. It may not work as well if you delay treatment.
Dosage is based on your medical condition and response to treatment. In children, dosage is also based on weight.
This medication works best when the amount of drug in your body is kept at a constant level. Therefore, take this drug at evenly spaced intervals. To help you remember, take it at the same times each day.
Continue to take this medication until the full prescribed amount is finished. Do not change your dose, skip any doses, or stop this medication early without your doctor’s approval.
Tell your doctor if your condition persists or worsens.
From: http://www.webmd.com/drugs/2/drug-941/acyclovir-oral/details#uses
2. Case Report

Acyclovir Nephrotoxicity: A Case Report Highlighting the Importance of Prevention, Detection, and Treatment of Acyclovir-Induced Nephropathy

1Internal Medicine, University of Texas Health Science Center, San Antonio, TX 78229, USA
2Division of Hospital Medicine, University of Texas Health Science Center, San Antonio, TX 78229, USA
Received 9 March 2010; Revised 22 July 2010; Accepted 16 August 2010
Academic Editor: Thomas Quaschning
Copyright © 2010 Raymond Fleischer and Michael Johnson. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Acute kidney injury is an unfortunate complication of acyclovir therapy secondary to crystal-induced nephropathy. It is characterized by a decrease in renal function that develops within 24–48 hours of acyclovir administration indicated by a rapid rise in the serum creatinine. Failure to quickly realize this as an etiology of acute kidney injury can lead to excessive morbidity to the patient. The case described in this vignette is an example of the clinical manifestation of acyclovir crystal obstructive nephrotoxicity. We will briefly discuss the pathophysiology, diagnosis, prevention, and management of patients that present with acyclovir nephrotoxicity.

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