Antiviral — nucleoside analogue (herpes zoster treatment)

Aciclovir 800mg Tablets (Ramsay Hunt Syndrome / Herpes Zoster Oticus)

Brand names: Zovirax, Aciclovir generic

Used in: Meningitis & Encephalitis Acute Red Eye

Aciclovir is an antiviral used for herpes simplex and varicella-zoster (chickenpox and shingles) infections.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It is activated by viral thymidine kinase and then inhibits viral DNA polymerase, selectively blocking viral DNA replication.

Prescribing in practice

Start it early (e.g. within 72 hours of a shingles rash) for benefit.
It is renally cleared — reduce the dose in renal impairment and ensure good hydration, especially with intravenous use (risk of crystal nephropathy and neurotoxicity).
It is generally well tolerated by mouth.

Monitoring

For intravenous or high-dose use monitor renal function and hydration.

Counselling the patient

Start it as early as possible.
Drink plenty of fluids.
Complete the course.

Evidence & guidelines

Standard treatment for significant herpes simplex and varicella-zoster infection, most effective when started early, with renal dose adjustment.

Reference: NICE CKS Shingles; ENT-UK Ramsay Hunt Guidelines; Cochrane Review Zoster; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways