Acyclovir During Pregnancy: Safety, Risks, And Precautions

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If you are diagnosed with herpesiXA viral, contagious infection that causes sores and blisters on the genitals or in the mouth. simplex or varicella-zoster virus (chickenpox)iXA viral infection characterized by fluid-filled blisters, itchy rash, or fever. during your prenatal checkups, or if you have a history of recurrent genital herpes, your doctor may recommend antiviral medicines such as Acyclovir during pregnancy.

Herpes simplex, sometimes known as herpes, is a common viral infection. The fetus is at risk of acquiring neonatal herpes if the pregnant mother has this illness. While herpes is unlikely to be transferred in the uterus, it can be passed on to the newborn during vaginal delivery. Therefore, proper diagnosis and treatment are critical.

This post discusses whether Acyclovir is safe to take during pregnancy, the risks involved, and some frequently asked concerns.

In This Article

What Is Acyclovir?

Acyclovir during pregnancy

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Acyclovir is an antiviral medication useful for treating and preventing recurrence of cold thrushiXA fungal infection identified as creamy, white lesions on the tongue or cheeks. , genital herpes (caused by herpes simplex virus 2) and chicken pox and shinglesiXA viral infection in those with a prior history of chicken pox, characterized by painful and blistering rashes.  (caused by the varicella-zoster virus). It is also approved for those with a weak immune system such as HIV.

Doctors prescribe antiviral drugs such as acyclovir to suppress the outbreak of genital lesion. Though it does not eliminate the viruses, it reduces the intensity and severity of the symptoms, and shorten the duration of the outbreaks.

Acyclovir is sold under the brand name Zovirax and is available in the form of oral tablets, intravenous injections, and topical ointments (1).

Can You Take Acyclovir (Zovirax) During Pregnancy?

Can You Take Acyclovir (Zovirax) During Pregnancy?

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You may take acyclovir if your doctor prescribes it. But do not take it without prescription or proper consultation.

The US Food and Drug Administration (FDA) has classified acyclovir as pregnancy category B drug, which means the studies conducted on animals demonstrated low risk, but there are no adequate and well-controlled studies in pregnant women (1).

The American Sexual Health Association (ASHA) says that the FDA has not approved any drug for treatment of herpes during pregnancy. However, many physicians prescribe this acyclovir at the end of pregnancy if the potential benefits outweigh the potential risks (2).

The American Academy of Family Physicians has observed that using acyclovir in the first trimester did not increase fetal congenital abnormalities. It recommends acyclovir as the “antiviral drug of choice” in early pregnancy (3). Studies on the effects of acyclovir during second and third trimesters are limited (4).

protip_icon Point to consider
Small studies suggest that acyclovir taken during the last month of pregnancy may prevent herpes recurrences and, therefore, decrease the need for C-sections (2).

How Much Acyclovir Is Safe To Take During Pregnancy?

Your obstetrician/gynecologist will decide the dosage depending on the severity of the condition, overall maternal health, and other parameters (5). Doctors usually prescribe the medicine when you experience the first episode of herpes during pregnancy. They might ask you to take the medicine everyday in the last four weeks of pregnancy to reduce the risk of outbreak, and prevent transmission to the newborn.

There is theoretical risk of teratogenicity when used in the first trimester. When the patient presents within 24 hours of the onset of rash and gestation is more than 20 weeks, it can be used safely.

What If You Have Already Taken Acyclovir (Zovirax) During Pregnancy? 

If you have been on acyclovir even before your pregnancy, or have taken it without prescription, then let your doctor know about it. They can decide whether or not you should continue with the drug, or cut it down to the lowest possible dosage. Do not stop taking the medication suddenly.

What Could Be The Side Effects Of Acyclovir During Pregnancy?

Hairloss is a probable side effect of acyclovir

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The potential side effects of taking acyclovir include diarrhea, nausea, headache, fever, hair loss, and changes in vision. These symptoms resolve in a few days, and might not require a doctor’s attention.

However, you might have to see the doctor in the case of some serious side effects, such as (6)

  • Allergic reactions including itching, skin rash, swollen lips, tongue or faceConfusion, hallucinationsiXA phenomenon in which one may sense visuals, sounds, or smells that may seem real but, in reality, are not. , and tremors
  • Increased sensitivity to sunlight
  • Difficulty in passing urine
  • Chest pain
  • SeizuresiXAbrupt, uncontrollable physical movements and behavioral changes driven by irregular electrical activity in the brain.
  • Yellowing of skin or eyes
  • Difficulty in sleeping
  • Bloody diarrhea
  • Stomach pain or cramps
  • Numbness or tingling sensation in the arms or legs

protip_icon Quick fact
Other side effects of acyclovir may include fatigue, fever, headache, muscle pain, stomach upset, and low blood pressure (1).

General Precautions To Follow While Taking Acyclovir

Here are some precautions you may take to stay safe.

  • Tell your doctor if you have nerve, liver, kidney or electrolyte abnormalities.
  • Avoid taking the medication if you experience any symptoms of allergy.
  • Drink a lot of water when you are on medication.
Pregnant women on acyclovir should drink ample water

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  • Do not exceed the suggested dosage of the medication.

Next, we answer a few queries commonly asked by our readers.

Frequently Asked Questions

1. Does acyclovir affect the birth control pill?

There are no studies on the interaction between acyclovir and birth control pills, so your doctor might prescribe them together, if necessary.

2. Is it safe to use acyclovir (Zovirax) cream during pregnancy?

Yes, acyclovir cream is considered safe during pregnancy. It is often used to treat cold sores, where a small amount is applied to the affected area (7).

3. Does acyclovir cross the placenta?

Studies indicate that acyclovir can easily pass through the placental barrier (8).

4. Is acyclovir 400 mg safe during pregnancy?

It is safe to give 400 mg of acyclovir every eight hours to a pregnant woman. Study indicates that at this dosage, the drug can safely and effectively suppress herpes simplex virus recurrences during the final weeks of pregnancy (9).

5. What are the effects of acyclovir on a fetus?

Studies show no increase in congenital disabilities in fetuses exposed to acyclovir antiviral treatment. The rates and types of congenital disabilities observed in these pregnancies were not significantly different from those in the general population (10).

You should only take Acyclovir during pregnancy if your doctor recommends you. If they diagnose you with herpes simplex or varicella-zoster virus or you have a history of recurrent genital herpes, they may prescribe you the same. Also, if there is a genital lesion outbreak, your doctor may prescribe Acyclovir to protect your unborn baby. You may sometimes encounter some adverse effects when taking Acyclovir. So check with your doctor if your symptoms do not resolve after a few days or become severe.

Infographic: Potential Adverse Effects Of Acyclovir In Pregnant Women

Acyclovir is an antiviral medication that may be prescribed during pregnancy. However, you should be watchful about the side effects of this drug and not confuse them with general pregnancy discomforts. The infographic below lists some serious side effects of Acyclovir during pregnancy that require prompt medical intervention.

possible adverse effects of acyclovir during pregnancy(infographic)

Illustration: Momjunction Design Team

Get high-quality PDF version by clicking below.

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Download Infographic in PDF version

Did you take acyclovir during pregnancy? Share your experiences with us in the comments section below.

This post is for informational purposes only and is not a replacement for a doctor’s consultation. Do not use any medication without talking to your doctor. 

Key Pointers

  • Acyclovir is an antiviral medication that is used to treat chickenpox, herpes simplex, and shingles.
  • It is classified by the FDA as pregnancy category B, and there is limited information available regarding its safety during pregnancy.
  • The appropriate dosage of acyclovir during pregnancy is determined by a physician and is based on factors such as the severity of the illness.
  • Doctors may prescribe acyclovir during the final four weeks of pregnancy to prevent transmission of the disease to the newborn.
  • Possible side effects of taking acyclovir include diarrhea, nausea, headache, fever, hair loss, and changes in vision.

Empower yourself with knowledge by watching this video, specifically designed for pregnant individuals diagnosed with herpes. It offers comprehensive guidance on safeguarding both yourself and your baby during this crucial time.


MomJunction's articles are written after analyzing the research works of expert authors and institutions. Our references consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Prescribing Information; Zovirax (acyclovir sodium); US Food & Drug Administration.
3. Acyclovir Safe for Treating Herpes Infection in Early Pregnancy; American Academy of Family Physicians
5. Management of Genital Herpes in Pregnancy; Royal College of Obstetricians and Gynaecologists (2014)
6. Acyclovir; US National Library of Medicine; 2017
7. Cold sores in Pregnancy and Breastfeeding; NSW Medications in Pregnancy and Breastfeeding Service; 2016
8. G I Henderson etal.; Acyclovir transport by the human placenta; National Library of Medicine, NCBI (1992)
9. L M Frenkel et al.; Pharmacokinetics of acyclovir in the term human pregnancy and neonate; National Library of Medicine, NCBI (2004)
10. Katherine M Stone et al.; Pregnancy outcomes following systemic prenatal acyclovir exposure; National Library of Medicine, NCBI (2004)
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