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Aciclovir

Medication antiviral other
Aka: acyclovir, Zovirax
Brands seen in Singapore: Zovirax, Virox, Herperax, Avorax, Virless
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
NHS: cold sores, shingles, chickenpox, genital herpes
When to take
NHS: started as early as possible after it is prescribed
Take with
NHS: plenty of water, especially with kidney problems
Pros & cons
Pros
  • NHS: most adults can use it; children usually the cream
  • NHS: comes as tablets, cream and eye ointment
  • NHS: nothing known to affect the cream or eye ointment
Cons
  • NHS: headache, dizziness, nausea, diarrhoea, rash
  • NHS: rare liver, kidney and blood-cell problems
  • SG register: all 34 SG rows are prescription only
Sources
  1. HSA — Listing of Registered Therapeutic Products (data.gov.sg dataset d_767279312753558cbf19d48344577084), Forensicclassification column; all 5,511 rows cached at /tmp/hsa_all.json and filtered locally (not re-fetched), 34 aciclovir/acyclovir rows (valaciclovir excluded), 27 Aug 2026 · read 2026-08-27
    what it says
    “ZOVIRAX CREAM 5% w/w SIN01191P · VIROX TABLET 400 mg SIN11658P · HERPERAX SIN09393P · AVORAX SIN09254P · VIRLESS SIN08532P — ATC J05AB01 and D06BB03; all 34 rows read Forensicclassification "Prescription Only"”
  2. NHS medicines A–Z — Aciclovir (Zovirax): what aciclovir is for (reviewed 23 February 2026) · read 2026-08-27
    what it says
    “Aciclovir is an antiviral medicine used to treat certain infections … cold sores; shingles; chickenpox; genital herpes; herpes simplex eye infections”
  3. NHS medicines A–Z — Aciclovir: how to use aciclovir · read 2026-08-27
    what it says
    “start taking the tablets as soon as possible after you've been prescribed them … drink plenty of water while taking aciclovir tablets – this is particularly important if you have kidney problems”
  4. NHS medicines A–Z — Aciclovir: side effects · read 2026-08-27
    what it says
    “Common side effects of aciclovir tablets include: headache; feeling dizzy or faint; feeling sick (nausea) or being sick (vomiting); diarrhoea; stomach ache; a rash … problems with your liver … problems with your kidneys … changes with your blood cells”
  5. NHS medicines A–Z — Aciclovir: who can and cannot use aciclovir · read 2026-08-27
    what it says
    “Most adults can use aciclovir. Children can usually use the cream or ointment … you may not be able to use it if you've had an allergic reaction to aciclovir or a similar medicine called valaciclovir in the past.”
  6. NHS medicines A–Z — Aciclovir: using aciclovir with other medicines, food and drink · read 2026-08-27
    what it says
    “No medicines are known to affect aciclovir cream or eye ointment … These include: probenecid (a medicine used to treat gout); cimetidine … mycophenolate mofetil”
  7. US label for acyclovir tablets (effective 2026-02-04) via openFDA drug/label.json, Dosage and Administration · read 2026-08-27
    what it says
    “Acute Treatment of Herpes Zoster: 800 mg every 4 hours orally, 5 times daily for 7 to 10 days. Genital Herpes: Treatment of Initial Genital Herpes: 200 mg every 4 hours, 5 times daily for 10 days.”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.