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Acyclovir (antiviral agent)

Uses|Precautions & warnings|Side effectsMouth pain|Interactions|Dosage

Acyclovir is an antiviral drug that has several brands. It is useful for treating a variety of viral infections. In addition, acyclovir only works for viral infections, not fungal or bacterial infections.

acyclovir

Uses

What is acyclovir used for?

This drug treats several infections caused by herpes viruses, including:

  • Herpes simplex infections (oral, skin, and genital herpes)
  • Varicella infection (chickenpox)
  • Herpes zoster (shingles)

How should I take acyclovir?

Read the directions on the packaging for complete information. Check the label and expiration date.

Take the tablet by mouth. Swallow it whole without chewing, crushing, or swallowing it. Drink plenty of water while taking this drug to prevent kidney injury.

How do I store Acyclovir?

This product is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store it in the bathroom or the freezer.

There may be different brands of this drug that may have different storage needs. So, it is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush this product down the toilet or pour them into a drain unless instructed to do so. Additionally, it is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using acyclovir?

Before using this drug, tell your doctor if you are/have:

  • Pregnant or breastfeeding.
  • Taking any other medicines. This includes any prescription, OTC, and herbal remedies.
  • An allergy to any of the ingredients of this product, especially milk products.
  • Any other illnesses, disorders, or medical conditions.
  • Weight loss or gain.

Herpes can be passed to your baby during childbirth if you have a genital lesion when your baby is born. If you have genital herpes, it is very important to prevent herpes lesions during pregnancy. Take your medicine as directed to best control your infection.

Herpes infections are contagious and you can infect other people, even while you are being treated. Avoid letting infected areas come into contact with other people. Avoid touching an infected area and then touching your eyes. Wash your hands frequently to prevent passing the infection to others.

Taking this medicine will not prevent you from passing genital herpes to your sexual partner. Avoid sexual intercourse while you have active lesions or the first symptoms of an outbreak. Genital herpes may still be contagious through “viral shedding” from your skin, even if you have no symptoms.

Is it safe during pregnancy or breastfeeding?

Unfortunately, there isn’t enough information about the safety of using this drug during pregnancy and breastfeeding. Acyclovir passes into breast milk and may affect a nursing infant. Please always consult with your doctor to weigh the potential benefits and risks before taking any medication.

This medication is pregnancy risk category B according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effectsMouth pain

What side effects can occur from acyclovir?

Like all drugs, this product may have side effects. If they occur, side effects are generally mild and resolve once treatment is finished or the dose is lowered. Some reported side effects include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Malaise
  • Headache
  • Mouth pain (while using an acyclovir buccal tablet)

Get emergency medical help if you have any of these signs of an allergic reaction to acyclovir such as hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have:

  • Easy bruising or bleeding
  • Purple or red pinpoint spots under your skin
  • Signs of a kidney problem such as little or no urinating, painful or difficult urination
  • Swelling in your feet or ankles
  • Feeling tired or short of breath

However, not everyone experiences these side effects. In addition, some people may experience other side effects. So, if you have any concerns about a side effect, please consult your doctor or pharmacist.

Interactions

What drugs may interact with acyclovir?

This medication may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects.

To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist.

Drugs with known interactions:

  • Probenecid
  • Cimetidine
  • Mycophenolate mofetil
  • Cyclosporine
  • Tacrolimus

If you experience an adverse drug interaction, stop taking this drug and continue taking your other medication. Inform your doctor immediately to reevaluate your treatment plan. Approaches include dose adjustment, drug substitution, or ending therapy.

Does food or alcohol interact with acyclovir?

This drug may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with acyclovir?

This drug may interact with underlying conditions. This interaction may worsen your health condition or alter the way the drug works. Therefore, it is important to always let your doctor and pharmacist know all the health conditions you currently have, especially:

  • Kidney disease
  • Compromised immunity or immunosuppression

Dosage

The information provided is not a substitute for any medical advice. Therefore, you should always consult with your doctor or pharmacist before using any medication.

What is the dose for an adult?

Genital herpes

Initial treatment is 200 mg orally every 4 hours while awake (5 times daily) for 10 days or 400 mg orally every 8 hours for 7-10 days.

Intermittent treatment for recurrence is 200 mg orally every 4 hours while awake (5 times daily) for 5 days; initiate at the earliest sign or symptom of recurrence.

Chronic suppression for recurrence is 400 mg orally every 12 hours for up to 12 months; alternatively, 200 mg 3-5 times daily.

Herpes Simplex Virus Encephalitis

The recommended dose is 10-15 mg/kg IV every 8 hours for 10 days; up to 14-21 days reported.

In obese patients, calculate the dose using body mass.

Mucocutaneous Herpes Simplex Virus Infection

Treatment in immunocompromised patients

IV: The recommended dose is 5 mg/kg every 8 hours for 7 days; dosing up to 14 days reported.

In obese patients, calculate the dose using body mass.

Herpes Zoster (Shingles)

Acute treatment: The recommended dose is 800 mg by mouth every 4 hours while awake (5 times daily) for 7-10 days.

Immunocompromised patients

  • The recommended dose is 10 mg/kg IV every 8 hours for 7 days.
  • In obese patients, use IBW.
  • CrCl: 25-50 ml/min: Full recommended IV dose is every 12 hours;
  • 10-25 ml/min: Full recommended IV dose is once daily;
  • 0-10 ml/min: 50% of recommended IV dose is once daily.

Varicella-Zoster (Chickenpox)

>40 kg (immunocompetent): The recommended dose is 800 mg orally every 6 hours for 5 days.

Immunocompromised patients: The recommended dose is 10-15 mg/kg IV every 6 hours for 7-10 days.

In obese patients, calculate the dose using body mass.

What is the dose of acyclovir for a child?

Neonatal Herpes Simplex Virus Infection

The recommended dose is 30 mg/kg/day IV divided every 8 hours for 14-21 days; alternatively, 20 mg/kg IV every 8 hours for 14-21 days.

In obese patients, calculate the dose using body mass.

Herpes Simplex Virus Encephalitis

3 months-12 years: The recommended dose is 20 mg/kg IV every 8 hours for 10 days; up to 14-21 days reported.

>12 years: The recommended dose is 10-15 mg/kg IV every 8 hours for 14-21 days.

In obese patients, calculate the dose using body mass.

Mucocutaneous Herpes Simplex Virus Infection

Treatment in immunocompromised patients

<12 years: The recommended dose is 10 mg/kg IV every 8 hours for 7 days.

>12 years: The recommended dose is 5-10 mg/kg/day IV divided every 8 hours for 5-7 days; up to 14 days reported.

In obese patients, calculate the dose using body mass.

Herpes Zoster (Shingles)

Less than 12 years (immunocompromised): The recommended dose is 20 mg/kg IV every 8 hours for 7 days.

More than 12 years (immunocompetent): The recommended dose is 800 mg PO every 4 hours while awake (5 times daily) for 7-10 days

More than 12 years (immunocompromised): The recommended dose is 30 mg/kg/day IV divided every 8 hours for 7-10 days

In obese patients, calculate the dose using body mass.

Varicella-Zoster (Chickenpox)

≥2 years and <40 kg: The recommended dose is 20 mg/kg/dose by mouth every 6 hours for 5 days; not to exceed 800 mg/dose.

>40 kg: The recommended dose is 800 mg by mouth every 6 hours for 5 days.

In obese patients, calculate the dose using body mass.

Immunocompromised patients

  • <12 years: The recommended dose is 20 mg/kg/dose IV every 8 hours for 7 days.
  • >12 years: The recommended dose is 10 mg/kg/dose IV every 8 hours for 7 days.

How is Acyclovir available?

Acyclovir is available in the following brands, dosage forms, and strengths:

  • Acycla cream 5% w/w
  • Herpex oral suspension 200 mg/5 mL
  • Herpex tablet 200 mg, 400 mg, 800 mg
  • Virest Cream 5% w/w
  • RiteMED Aciclovir tablet 400 mg, 800 mg
  • Zovirax, powder for injection, 250 mg vial
  • Zovirax tablet 200 mg, 400 mg, 800 mg
  • Zylovir tablet 200 mg, 400 mg, 800 mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to the nearest emergency room.

What should I do if I miss a dose?

If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

Sources

Acyclovir (Oral Route, Intravenous Route) https://www.mayoclinic.org/drugs-supplements/acyclovir-oral-route-intravenous-route/precautions/drg-20068393?p=1 Accessed June 11, 2021

Drug Database: Acyclovir https://clinicalinfo.hiv.gov/en/drugs/acyclovir/patient Accessed June 11, 2021

Acyclovir https://www.ncbi.nlm.nih.gov/books/NBK542180/ Accessed June 11, 2021

Acyclovir https://pubchem.ncbi.nlm.nih.gov/compound/Acyclovir Accessed June 11, 2021

Aciclovir (including Zovirax) https://www.nhs.uk/medicines/aciclovir/ Accessed June 11, 2021

Zovirax https://www.mims.com/philippines/drug/info/zovirax Accessed June 11, 2021

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Written by Stephanie Nicole Nera, RPh, PharmD Updated Jun 13
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