Acyclovir During Pregnancy: Safety, Risks, And Precautions

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If you are diagnosed with herpes simplex or varicella-zoster virus (chickenpox) 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 baby is at risk of acquiring neonatal herpes if the 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.

What Is Acyclovir?

Acyclovir is an antiviral medication useful for treating and preventing recurrence of cold thrush, genital herpes (caused by herpes simplex virus 2) and chicken pox and shingles (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?

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 the use of acyclovir in the first trimester did not increase birth defects. 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).

How Much Acyclovir Is Safe To Take During Pregnancy?

Your doctor will decide the dosage depending on the severity of the condition 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 teratogenecity when used in 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?

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, hallucinations, and tremors
  • Increased sensitivity to sunlight
  • Difficulty in passing urine
  • Chest pain
  • Seizures
  • Yellowing of skin or eyes
  • Difficulty in sleeping
  • Bloody diarrhea
  • Stomach pain or cramps
  • Numbness or tingling sensation in the arms or legs

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 the medication.
  • 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)

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.

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. 


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
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shreeja pillai

Shreeja holds a postgraduate degree in Chemistry and diploma in Drug Regulatory Affairs from the University of Mumbai. Before joining MomJunction, she worked as a research analyst with a leading multinational pharmaceutical company. Her interest in the field of medical research has developed her passion for writing research-based articles. As a writer, she aims at providing informative articles on health... more

Subhashis Samajder

( MS, DNB)
Dr. Subhashis Samajder is a consultant Gynecologist-Obstetrician currently practising at Narayana Multispeciality Hospital, Howrah. His area of expertise includes abortion, colposcopy surgery, hysterectomy, hysteroscopy, infertility treatment, and menopausal problems. Dr. Samajder believes in sending his patients back home healthy and satisfied with the treatment. He also takes up women’s health awareness through his YT videos.