4 Zovirax Uses & Side Effects

Zovirax (acyclovir) is an antiviral drug used to treat infections caused by herpes viruses, including genital herpes, shingles (herpes zoster), and chickenpox (varicella). Please continue reading to learn more about its uses and side effects.

What is Zovirax? How does it work?

Zovirax is a brand name product for the generic drug acyclovir. It belongs to a group of medications called antivirals. Specifically, acyclovir acts as a synthetic purine nucleoside analogue that is active against herpes simplex virus types 1 (HSV-1), type 2 (HSV-2), and varicella-zoster virus (VZV).

Zovirax is used to treat herpes infections. It works by stopping the spread of the herpes virus in the body by interfering with DNA polymerase, a protein that is vital for the replication process where the virus makes copies of itself.

Zovirax has been shown to reduce viral shedding, and one hope in the treatment of genital herpes is that decreasing viral shedding would lead to a reduction in the rate of passing genital herpes during sexual contact. However, it is important to know that the link between reducing viral shedding and decreasing the risk of spreading herpes has not been established yet.

The takeaway is that while Zovirax and other antiviral therapies can be used to relieve the painful symptoms of an active herpes infection and prevent herpes lesions, these antiviral medications will not cure herpes.

What is Zovirax used to treat?

Zovirax (generic form: acyclovir) is used to treat:

Varicella (chickenpox)
Herpes zoster (shingles)
Herpes simplex virus type 1 (oral herpes or cold sores) and herpes simplex virus type 2 (genital herpes)
Recurrent herpes simplex labialis (oral herpes or cold sores)

Oral hairy leukoplakia (OHL) is a condition causing white patches on the tongue that is triggered by the Epstein-Barr virus. OHL mostly occurs in HIV (human immunodeficiency virus) patients whose immune systems are compromised. Systemic antiviral therapy with oral Zovirax (acyclovir) and Valtrex (valacyclovir) have been used to eliminate the lesions caused by OHL). However, relapse of this condition occurs once the antiviral medication is stopped. Therefore, further research is needed to assess the efficacy of acyclovir in treating oral hairy leukoplakia caused by the Epstein-Barr virus.

How to take Zovirax?

Zovirax comes in the form of an oral capsule, tablet, and oral suspension to be taken by mouth. It is also available as a delayed-release buccal tablet and as a cream and ointment for topical application to sores and blisters.

Take oral acyclovir (tablets, capsules, or liquid suspension) by mouth with or without food. The treatment duration will depend on the condition being treated. You will need to take the medicine 3-5 times every day at evenly spaced intervals. Start treatment with Zovirax as soon as symptoms begin.
For example, to treat the initial genital herpes infections, the dosage for Zovirax is 200 mg orally 5 times daily for 10 days, or 400 mg orally 3 times daily for 7 to 10 days.
If you are prescribed Zovirax to prevent outbreaks of genital herpes, the dosage of Zovirax is 400 mg orally for up to 12 months.
Your doctor will provide you with instructions on the dosage and duration of therapy.
Use the dosing syringe or medicine dose-measuring device provided to measure the dose of the oral suspension. Do not use a regular household spoon as this can result in inaccurate dosing.
Apply the delayed-release buccal tablet with a dry finger to your upper gum within one hour of developing cold sore symptoms (burning, itching, redness) and before the cold sore appears. This is a one-dose regimen, and it is very important that it is used at the first sign of symptoms before the cold sore becomes visible. Do not crush, chew, suck, or swallow the delayed-release buccal tablet. Also, do not wear upper dentures or brush your teeth until the tablet dissolves completely. You can rinse your mouth gently if you need to while the tablet is in place.
Zovirax cream and ointment are for external use only on herpes lesions. These products can speed up healing and reduce symptoms. Apply the cream or ointment immediately as soon as a genital lesion or cold sore appears. Do not apply these products inside the mouth or vagina.

Read the prescription label carefully and take or use acyclovir exactly as directed by your healthcare professional. Do not change the dose, dosage frequency, or duration of treatment without consulting your healthcare provider.

What is the dose of Zovirax?

The usual acyclovir doses are as follows:

Herpes zoster (shingles): 800 mg orally 5 times a day for 7-10 days.
Genital herpes: 200 mg 5 times a day for 10 days, or 400 mg orally 3 times daily for 7 to 10 days.
Chronic suppressive therapy for recurrent genital herpes infections: 400 mg orally 2 times a day for up to 12 months.
Chickenpox in children 2 years of age and older: 20 mg/kg per dose by mouth 4 times a day for 5 days.
Chickenpox in adults and children with a body weight over 40 kg: 800 mg orally 4 times a day for 5 days.

What is a common side effect of Zovirax?

A common side effect of Zovirax is mild skin pain (with topical products). Oral Zovirax can cause side effects such as diarrhea, nausea, vomiting, upset stomach, tiredness, headache, and mouth pain with buccal tablets. Call your doctor for medical advice about side effects if they are severe or persist after a few days when your body has had a chance to get used to the medicine.

What are the serious side effects of Zovirax?

More serious side effects of Zovirax are listed below. Tell your doctor immediately or seek emergency medical help if you develop the following signs and symptoms:

Severe allergic reaction: skin rash, hives, itching, difficulty breathing or swallowing
Signs of kidney injury: swelling in the ankles or feet, blood in urine, painful or difficult urination
Unusual changes in mood and behaviors: confusion, hallucinations, agitation, aggression, difficulty speaking or moving
Low in red blood cells: weakness, fatigue, pale skin
Stevens-Johnson syndrome: a rare, serious allergic skin reaction
Liver problems: unusual bleeding or bruising, stomach pain or stomach cramps
Vision changes
Seizures
Loss of consciousness

What are the precautions with Zovirax use?

Allergic reactions

Tell your doctor if you have ever had an allergic reaction to acyclovir (Zovirax), other antiviral drugs such as valacyclovir, or any other medications.

You should not take the buccal tablets (Sitavig) if you are allergic to milk protein.

Drug interactions

Taking acyclovir with certain other drugs can increase the risk of serious adverse effects. Give your doctor or pharmacist a complete list of your medications, including prescription drugs, over-the-counter medications, dietary supplements, and herbal products. This can help avoid interactions between Zovirax and your other medications. Specifically, tell your doctor if you are taking the following type of medication to avoid drug interactions leading to serious adverse effects:

Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs)
Certain antibiotics
Cancer therapy
Medication for osteoporosis treatment

Medical conditions

Tell your doctor if you have ever had kidney disease, for if you have a medical condition that causes a weak immune system such as HIV/AIDS.

Missed dose

If you miss a dose of Zovirax, take it or use it as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose or use extra medicine to make up for a missed dose.

Overdose

In case of an overdose, call your doctor immediately or seek emergency medical help. You can also call your local poison control center or the national poison control center at 1-800-222-1222.

Storage

Store at room temperature, safely out of reach of children and pets.

Sexual activity

You can spread genital herpes to a sexual partner even if you are taking acyclovir to treat genital herpes and even if you don't have visible blisters. Avoid sexual intercourse until 1-2 days after all your sores have healed. Talk to your healthcare provider about how to reduce the risk of transmission of genital herpes, along with information about testing and treatment for sexual contact.

Pregnancy and breastfeeding

Let your doctor know if you are pregnant or breastfeeding.

If you have genital herpes and get pregnant, let your doctor know so you can start taking medication to prevent a herpes outbreak. It is important to take Zovirax (acyclovir) as directed because herpes can be transmitted to your baby during childbirth if a genital lesion is present.

You should discuss with your doctor regarding the risks and benefits of using Zovirax (acyclovir) while breastfeeding, as it may not be safe.

When should you not use Zovirax?

You should not use Zovirax if you have had an allergic reaction to this medication in the past, or if you have a milk protein allergy, then Sitavig buccal tablets may not be the safe choice for you.

Older adults, people with kidney problems, and those with a high risk for dehydration should talk to their doctor before starting Zovirax treatment. Older adults are more likely to have side effects such as drowsiness, confusion, and hallucinations. People with reduced kidney function may be prescribed a lower dose of the medicine.

This medication should not be given to children younger than 2 years old.

Why was Zovirax discontinued?

A few acyclovir brand name products have been discontinued and withdrawn from the market. For example, Zovirax 200 mg oral capsules were discontinued and withdrawn from sale, but the U.S. Food and Drug Administration (FDA) confirmed that this product discontinuation was not due to concerns about safety or effectiveness. Similarly, Avaclyr (acyclovir eye ointment) was withdrawn from the market by the manufacturers due to marketing and supply chain challenges.

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