Aciclovir (tablets)

Sounds like 'ay-SYE-kloe-vir'

Aciclovir tablets is used to treat infections caused by viruses. Find out how to take it safely and possible side effects. Aciclovir tablets is also called Lovir or Zovirax.

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

What is aciclovir?

Aciclovir is used to treat infections caused by viruses, such as herpes simplex virus (which causes cold sores around your mouth and genital herpes) and varicella zoster (which causes chickenpox and shingles). It works by stopping the growth of the viruses that cause the infection. 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 your body. Aciclovir is also used to prevent viral infections in people with a weakened immune system, such as if you are receiving cancer medication (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 until dissolved. This may make swallowing the tablets easier.
  • Timing: 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 in your body is kept at a constant level. You can take aciclovir with or without food.     
  • Drink plenty of water while taking aciclovir. It's important to drink plenty of water so you don't get dehydrated while taking aciclovir. This could affect your kidneys. This is especially important for older adults. 
  • Missed dose: If you forget to take your dose, take it as soon as you remember 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. Your doctor will advise you on how long to take aciclovir for (usually 5 to 10 days).

Precautions – before taking aciclovir

  • Are you pregnant or breast-feeding?
  • Do you have any kidneys problems?
  • Are you taking any other medicines? This includes any medicines you buy without a prescription, such 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.

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 (runny poos)    
  • This may settle after a few days.
  • Tell your doctor if troublesome.
  • Headache, feeling sleepy, dizzy or tired
  • 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 your lips, face, and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116.
*Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product


Aciclovir may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting aciclovir or before starting any new medicines.

Learn more

The following links has more 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: Angela Lambie, Pharmacist, Auckland Last reviewed: 19 Dec 2018