Aciclovir
Also known as: Zovirax
What it's for
Aciclovir is an antiviral for cold sores, genital herpes, shingles, and chickenpox. It does not cure herpes but helps heal outbreaks faster and reduces their severity.
Comes as: Tablets, cream, or liquid
How to take it
- For cold sores: Apply cream 5 times daily for 5 days.
- For genital herpes: Usually 200mg 5 times daily for 5 days.
- For shingles: Usually 800mg 5 times daily for 7 days.
- Start treatment as soon as symptoms begin.
Doses here are typical. Always follow the instructions from your prescriber or on the packet — they come first.
Common side effects
- Feeling sick
- Headache
- Dizziness
- Stomach pain
The leaflet inside the packet lists all known side effects.
Important safety points
- Start treatment at the first sign of symptoms for best effect
- Drink plenty of water when taking tablets
- Cold sore cream is for lips only - not for genital herpes
- Tell your doctor if you have kidney problems
Get medical help urgently if…
- You have confusion or hallucinations
- You have difficulty passing urine
- You have a severe skin reaction
- You have signs of an allergic reaction
Call NHS 111 for urgent advice, or 999 if someone is seriously unwell.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.