Report on Acyclovir Side Effects and Usage by AskDocWeb

About Acyclovir

Picture of Acyclovir

What is Acyclovir?

Acyclovir (ay-SYE-kloe-veer) is an antiviral used to treat shingles, chickenpox, and genital herpes ( which can cause painful lesions and blisters ), herpes simplex and herpes zoster. Antivirals work for only one kind or group of virus infections.

Acyclovir can help those with HIV live longer by preventing herpes simplex outbreaks. Acyclovir is also used to treat a viral infection that shows up on the sides of the tongue, called lenkoplakia and widespread herpes virus infections in newborns. It does not cure herpes, but does help relieve the pain and sores heal faster.

Acyclovir works against HSV type 1, 2, and VZV. Acyclovir is considered the drug of choice for treatment of mucosal or cutaneous HSV infections caused by HSV 1 and 2 in immunocompromised patients. It’s also used for treatment of severe first episodes of genital herpes infections, for herpes encephalitis; for neonatal herpes infections and for treatment of varicella-zoster infections.

Glaxo-Wellcome, Inc. makes Zovirax. They have an HIV patient assistance program you can reach by calling 800-722-9294. The pills come in 200 mg. 400 mg. and 800 mg. doses.

How does Acyclovir work?

Acyclovir interferes with the enzymes the virus needs for replication of DNA in cells and prevents the virus from multiplying. It is also incorporated into the virus DNA chain which terminates replication.

How Long does it take?

Typically you can expect the crusting over and healing of herpes sores in a few days. If you have chronic outbreaks of herpes, you may require acyclovir for long-term therapy.

What side effects do users of Acyclovir report?

Side effects, that may go away during treatment, include nausea, vomiting, diarrhea, or headache. If they continue or are bothersome, check with your doctor. Some people have reported hair loss (alopecia) from prolonged use. Others have reported dizziness, fatigue, skin rash, anorexia, leg pain, medication taste, pale stools and sore throat. An uncommon side effect is hypersensitivity to sunlight called photosensitivity that results in a rash when skin is exposed to sunlight.

The digestive side effects are reduced if taken with meals. Some nausea can be avoided with eating strategies like eating dry salted crackers and not lying down after you eat.

Stomach pain and cramps are listed as possible side effects of Acyclovir that should be reported to your doctor.

Medications found helpful in reducing nausea include Compazine, Reglan, and Phenergan. Aspirin or other pain pills may help with headaches. Your dosage can be adjusted if your side effects are severe.

What are the symptoms of overdose or something gone wrong?

An overdose is not likely to be life threatening. If overdose is suspected, contact your local poison control center or emergency room immediately. Symptoms of an overdose include hallucinations, seizures, and kidney damage (decreased urine production).

If you miss a dose of Acyclovir

Do not miss any doses. If you miss a dose of this medicine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.

Conditions you should tell your Doctor about before taking Acyclovir:

Inform your doctor of any other medical conditions such as, allergies to foods, sulfites or other preservatives.

The CDC puts Acyclovir in Pregnancy Category B. If you are or may be pregnant, or if you plan on becoming pregnant, discuss with your doctor the benefits and risks of using this medicine during pregnancy.

This medicine is excreted in breast milk. If you are or will be breast-feeding while you are using this medicine, check with your doctor or pharmacist to discuss the risks to your baby.

Dehydration or kidney disease can increase blood levels of acyclovir, which would increase the chance of side effects.

Tell Your Doctor if you’re taking any of the following medicines:

Any medicine for infection or

Carmustine (BiCNU)

Cisplatin (Platinol)

Combination pain medicine containing acetaminophen and aspirin (Excedrin)

Cyclosporine (Sandimmune)

Deferoxamine (Desferal)


Gold salts (medicine for arthritis)

Inflammation or pain medicine

Lithium (Lithane)

Methotrexate (Mexate)


Nephrotoxic agents

Penicillamine (Cuprimine)

Plicamycin (Mithracin)


Streptozocin (Zanosar)

Tiopronin (Thiola)


Use of these medicines with acyclovir may increase the chance for side effects, especially for those with kidney disease.

Storing Acyclovir

Store this medicine at room temperature, away from light and moisture. Don’t store the capsule or tablet form of this medicine in the bathroom, near the kitchen sink, or in damp places. Heat and moisture cause the medicine to break down. When discarding medicine, make sure it’s out of the reach of children.

General Notes

Acyclovir should be taken with food and with a full (8 oz) glass of water. Not doing so may result in an upset stomach.

To clean up your infection completely, continue taking this medicine for the full course of treatment even if you feel better in a few days.

If you are using this medicine for genital herpes, begin using it as soon as you notice symptoms (pain, burning, blisters) of an infection.

Remember that although Acyclovir may reduce the chances of spreading herpes to others it does not completely eliminate that risk. Herpes of the genitals can be spread to your partner during any sexual activity. You can get herpes from a herpes infected partner even if your partner has no symptoms, but the infection is more likely to be spread if sores are present. This is true until the scabs have fallen off after the sores are completely healed. It’s best to avoid any sexual activity if either you or your partner has any symptoms of herpes. Use a condom (rubber) to help prevent the spread of herpes.

A limited number of studies have been done using acyclovir in children that resulted in the same effects as for adults. Talk to your doctor about this use of Acyclovir.

Acyclovir is also marketed under trade names such as Cyclovir, Herpex, Acivir, Acivirax(Mash-Premier), Zovirax, Aciclovir (Sanofi-Aventis) and Zovir (GSK). In Singapore, it is available in 400 mg as Avorax and 800 mg as Herperax.

Common Misspellings for Acyclovir

Acyclovir is often misspelled, as many people hear the word verbally, write it down and spell it incorrectly. Here are a few of the most common misspellings for Acyclovir: acclovir, acyclovir, ayclovir, acyclovr, acycloir, acyclvir, acycovir, acylovir, acycrovir, acyclovil, acycrovil, acyclovri, acycloivr, acyclvoir, acycolvir, acylcovir, accylovir, aycclovir, cayclovir, acyclovi, and cyclovir.

Feedback about Acyclovir

Subject: What do I do?

I was recently diagnosed with Bell’s Palsy. I am taking Acyclovir 400 mg. 5x a day. I may be pregnant. What would you advise. My doctor said that trials have shown no harm to fetuses of animals. I am not reassured by this. Please help.


AskDocWeb: Here is some reading for you regarding acyclovir and pregnancy that may reassure you. The first is from the Center for Disease Control. You can search their website with the second link. The third tells about the use of Acyclovir in pregnancy for primary prevention of neonatal herpes.

Center for Disease Control

Search the CDC

Acyclovir in pregnancy

Subj: Acyclovir – Please Help!

With Shingles of the eye, how long a duration do you stay on the medication Acyclovir?

I’m currently on 800 mg, 5 times a day. So far I’ve taken 50 doses, and now I’m told to take another 80 doses. Is this the correct protocol?

Should I get a blood test during this treatment? Does this medication have any side effects on the liver (2 years ago I had an abscess on my liver).


AskDocWeb: Your doctor should decide the best dosage and treatment for your condition. We haven’t come across any references to liver problems, just the kidneys. (decreased urine production)

Subj: Suppression treatment

I have Herpes Simplex on my nose for fifteen years. It usually occurs 1 – 2 times per year. Some outbreaks are more severe than others. I have been prescribed Acyclovir for the outbreaks– 400 mg 3x’s per day for 5 days. From August to December I have had 4 outbreaks – 3 of which were severe. My doctor wants me to begin taking 2 pills per day every day to suppress these outbreaks. My question is will I become immune to the medication altogether and then what do I do?


AskDocWeb: We have not found evidence of anyone becoming immune to Acyclovir. If you have experience otherwise, please let us know.

Subj: Side Effects of Acyclovir
Date: 8/20/2003

I am taking acyclovir for bells palsy. Yours is the first website that has said anything regarding side effects about memory loss, difficulty with contacts, & numbness in legs and feet. Thank you so much, I thought I was going crazy.

Lea Ann

Subj: Long term use of Acyclovir
Date: 1/20/2004

My son was on acyclovir drop for the shingles of his eye from four years ago. Recently his doctor noticed some damage to my son’s cornea so that he prescribed Acyclovir tab 800 mg per day for one year. I am worried about this long duration of therapy. Do you recommend such long time treatment and would you please let me know about the complications of being on acyclovir for one year.


AskDocWeb: We make no recommendations about treatment on this website. This is a product research and review site. While we came across several cases where Acyclovir was used for long-term care, we found nothing about complications from such long-term use.

Subj: I recommend Acyclovir
Date: 2/19/2004

I have gotten herpes simplex 1 in and around my mouth since I was 8 years old. I am now 22 and have been having the most often and severe outbreaks I have ever had. I believe this is due to some serious stress issues in my life. My doctor started me on Acyclovir capsules 400mg 2x daily. It works wonderfully!!! I recommend Acyclovir to anyone who can use it. It cuts healing time from 2 weeks down to 1! Also, if I begin taking the medication when I first start feeling lethargic and start running a fever I can prevent the blisters from ever forming!


Subj: Acyclovir for Chicken Pox
Date: 2/21/2004

My wife and myself were treated for Chicken Pox with Acyclovir 800mg x 5 per day.
1) Is there any problem in treating Chicken Pox with this.
2) Is it better to avoid medicine and allow body to build up immunity by itself.
3) Will we have the Accured Immunity against Chicken Pox for the rest of life.


AskDocWeb: First, Acyclovir is a common treatment for chickenpox.
2. In our opinion, yes for children but not for adults. In adults, chickenpox is a serious disease and may be life threatening. You have an increased risk of encephalitis and pneumonia, both of which have a significant mortality risk.
3. Most people do seem to develop life-long immunity once they have had chickenpox.

Note: Aspirin has been associated with Reye’s syndrome. Doctors recommend using Tylenol for fever in children who have viral infections like chickenpox or influenza.

Subj: Recurring fever
Date: 4/2/2004
My daughter was born with the herpes virus due to my doctor’s error in judgement. She was admitted to the hospital at 4 days old, an IV was inserted into her hand and acyclovir was administered every 8 hours for two and a half weeks. She is now 2 years old and suffers from recurring fevers with blisters in her mouth, usually lasting about 3 – 5 days and the recurrance is about once a month. She’s been suffering with these recurring fevers since I can remember. The fever and lethargy are the only symptoms. I have taken her to her pediatrician and an infectious disease doctor and had her tested for just about everything under the sun with no findings. The infectious disease specialists tells me that these recurring fevers do happen in children from time to time with no cause and she may outgrow them. Do you know if acyclovir could have any side effect that lingers in children that have been given the medication in infancy or is the herpes virus recurring in a fever manifestation? Any light you can shed for me would be most helpful. Thank you.

AskDocWeb: This sounds like the typical effects of the herpes virus. Unfortunately there is no cure for it yet and symptoms do recur from time to time.

Subj: First herpes outbreak
Date: 6/2/2004
I have been taking Acyclovir now for about 9 days for my first herpes outbreak ever. My throat has been soar the whole time since I started taking it and now I woke up this morning and it was swollen shut! My “little punching bag” at the back of my throat is about 4 times the size it should be. Could this be due to the Acyclovir?

AskDocWeb: This is one of the signs of an allergic reaction. Please see your doctor immediately.

Subj: Acyclovir for chicken pox?
Date: 6/3/2004
My son has chicken pox broke out on Saturday, I am 32 and have never had them. I had the blood test and am not immune. My doctor prescribed Acyclovir as a preventive measure on Tuesday as it was too late for the immune globulin. Will Acyclovir prevent me from getting the chicken pox?


AskDocWeb: No. Acyclovir is not a vaccine. What it will do is speed the healing process and help your body resist the disease more effectively.

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