Aciclovir – Antiviral medication for herpes infections and cold sores.
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What is Aciclovir?
Aciclovir is an antiviral medication specifically designed to treat infections caused by herpes viruses, including cold sores, genital herpes, and shingles. It’s most effective when treatment begins early in the course of an outbreak.
Book an online consultation if you’re experiencing symptoms of a viral infection such as cold sores, unusual skin rashes, or recurrent painful blisters. Our GPs can assess your symptoms and determine if Aciclovir or other antiviral treatment is appropriate for your condition.
What is Aciclovir used for?
- Cold sores (herpes simplex)
- Genital herpes infections
- Shingles (herpes zoster)
- Chickenpox (in severe cases)
- Prevention of herpes recurrence
- Eye infections caused by herpes
- Herpes encephalitis (serious brain infection)
How does Aciclovir work?
An antiviral medication that interferes with viral DNA synthesis, preventing herpes viruses from multiplying and spreading to healthy cells.
Dosage and Administration
Adults
200-800 mg taken 2-5 times daily depending on condition. Topical cream applied 5 times daily for cold sores.
Children
Dose calculated based on weight and condition—usually 20 mg per kg of body weight.
Important Notes
- Start treatment as early as possible when symptoms begin.
- Take with plenty of water to prevent kidney problems.
- For topical cream: apply to clean, dry skin every 4 hours during waking hours.
- Complete the full course even if symptoms improve.
Side Effects
Common Side Effects
- Nausea and vomiting
- Diarrhoea
- Headache
- Dizziness
- Skin irritation (with topical use)
- Fatigue
Serious Side Effects
Seek immediate medical attention if you experience:
- Kidney problems (especially with IV use)
- Severe allergic reactions
- Blood disorders
- Neurological effects (confusion, hallucinations)
- Severe skin reactions
Important Warnings
- Drink plenty of fluids to prevent kidney damage, especially with high doses.
- Tell your GP if you have kidney problems—dose adjustment needed.
- Start treatment as soon as possible after symptom onset for best effectiveness.
- Not a cure—helps control symptoms and reduce duration of outbreaks.
- Does not prevent transmission of herpes to others.
Drug Interactions
Tell your GP if you're taking any of the following medications:
- Probenecid—may increase aciclovir levels and kidney toxicity risk.
- Mycophenolate—may increase levels of both medications.
- Nephrotoxic drugs—increased risk of kidney damage.
- Generally few significant interactions with other medications.
Frequently Asked Questions
How quickly does Aciclovir work for cold sores?
If started within 24 hours of symptom onset, it can reduce duration by 1-2 days and lessen severity. The sooner you start, the better it works.
Will Aciclovir cure my herpes infection?
No, there's no cure for herpes. Aciclovir helps control outbreaks, reduces symptoms, and can prevent recurrence, but the virus remains dormant in your body.
Can I use Aciclovir cream and tablets together?
Usually one or the other is prescribed, but in some cases your GP might recommend both. Always follow your specific prescription instructions.
How long should I take Aciclovir for prevention?
For prevention of recurrent herpes, treatment duration varies from 6-12 months or longer, depending on your individual situation and response.
Medically Reviewed by: Mohammed Hassan - Independent Prescriber
Last Updated: 2025-01-14