Aciclovir tablets

Sounds like 'ay-SYE-kloe-vir'

Easy-to-read medicine information about aciclovir – what is it, how to take aciclovir safely and possible side effects.

Type of medicine Also called
  • Antiviral - medication to treat infections caused by viruses
  • Lovir®
  • Zovirax®

What is aciclovir?

  • Aciclovir is used to treat viral infections caused by herpes simplex virus (such as cold sores around the mouth and genital herpes), and viral infections caused by varicella zoster (such as chickenpox and shingles).
  • It works by stopping the growth of the viruses that cause the infection. In this way aciclovir reduces the severity of the infection, and stops it from spreading. It helps the infection heal faster, and lessens pain and itching. Aciclovir does not kill the virus. The viruses that cause these infections continue to live in the body.
  • Aciclovir is also used to prevent viral infections in people with a reduced immune system such as if you are receiving chemotherapy.   
  • Aciclovir is available as tablets in different strengths (200 milligrams, 400 milligrams and 800 milligrams).


  • The dose of aciclovir will be different for different people, depending on the type of infection and whether it is used to treat or prevent an infection.  
  • Your doctor will calculate the dose suitable for you.
  • Usually the dose ranges from 200 milligrams to 800 milligrams taken 2 to 5 times a day.
  • Always take your aciclovir exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much aciclovir to take, how often to take it, and any special instructions.

How to take aciclovir

  • Swallow your aciclovir tablets with a glass of water.
  • If you have difficulty swallowing the tablets, they can be dissolved in water. Add the tablets to a small glass of water and stir. This may make swallowing the tablets easier.  
  • You can take aciclovir with or without food.
  • Separate your doses out evenly during the day. For example, if your dose is to be taken 5 times a day, take a dose about every 4 hours such as 7am, 11am, 3pm, 7pm and 11pm. Aciclovir works best when the amount of drug in your body is kept at a constant level.     
  • Drink plenty of water while taking aciclovir, to keep your kidneys working well (unless your doctor advises you otherwise). 
  • Your doctor will advise you on how long to take aciclovir for (usually 5 to 10 days).
  • If you forget to take your dose, take it as soon as you remember that day. But, if it is nearly time for your next dose, just take the next dose at the right time. Do not take double the dose.
  • Keep taking aciclovir until you finish all the tablets. Do not stop taking it, even if you feel better after a few days. This will prevent the infection from returning.

Precautions — before taking aciclovir

  • Are you are pregnant or breast-feeding?
  • Do you have any problems with the way your kidneys work?
  • Are you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines?
  • Have you have ever had an allergic reaction to a medicine?

If so, it’s important that you tell your doctor before you start taking aciclovir. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Possible side effects

Like all medicines, aciclovir can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Nausea (feeling sick) or vomiting
  • Try taking aciclovir after a meal
  • Tell your doctor if troublesome
  • Stomach pain
  • Diarrhoea (loose, watery stools)    
  • This may settle after a few days
  • Tell your doctor if troublesome
  • Feeling sleepy, dizzy, tried, drowsy
  • Be careful when driving or using tools until you know how this medicine affects you
  • Signs of an allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116


Aciclovir may interact with a few medications and herbal supplements, so check with your doctor or pharmacist.

Learn more

The following links provide further information on aciclovir. Be aware that websites from other countries may contain information that differs from New Zealand recommendations.

Lovir Medsafe NZ Consumer Medicine Information 

Aciclovir for viral infections Patient Info, UK

Credits: Sandra Ponen, Pharmacist. Reviewed By: Dr J Bycroft, GP Last reviewed: 12 Jan 2018