Antiviral — nucleoside analogue (herpes zoster treatment) Pregnancy: Use with caution — oral aciclovir used in pregnancy for zoster; benefits generally outweigh risks. Topical aciclovir considered safe.

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

Brand names: Zovirax, Aciclovir generic

Adult dose

Dose: 800 mg five times daily for 7 days

Route: Oral

Frequency: Five times daily (every 4 hours while awake; omit one night-time dose)

Max: 4000 mg/day (800 mg × 5)

Ramsay Hunt syndrome (herpes zoster oticus with facial nerve involvement): 800 mg 5 times daily for 7–10 days, ideally started within 72 hours of rash onset. Combine with prednisolone 40–60 mg once daily for 7 days (tapered) for best facial nerve outcomes. If unable to swallow: IV aciclovir under specialist care. Adequate hydration essential to reduce nephrotoxicity risk.

Paediatric dose

Route: Oral

Frequency: Five times daily

Max: 800 mg per dose

Ramsay Hunt in children: uncommon. Aciclovir 800 mg 5×/day for children ≥12 years (adult dose). Under 12 years: specialist guidance — weight-based dosing (250 mg/m² IV or specialist oral dosing). Varicella-zoster in immunocompromised children: IV aciclovir preferred.

Dose adjustments

Renal

eGFR 25–50: 800 mg every 8 hours. eGFR 10–25: 800 mg every 12 hours. eGFR <10: 800 mg every 24 hours. Ensure adequate hydration.

Hepatic

No dose adjustment required.

Clinical pearls

Start within 72 hours of rash for maximal benefit — delay beyond 72 hours reduces efficacy significantly
Always combine with systemic corticosteroids (prednisolone) for Ramsay Hunt — combined therapy superior to antiviral alone for facial nerve recovery
Valaciclovir 1 g TDS for 7 days is an alternative with better bioavailability and simpler regimen (once licensed)
Ramsay Hunt carries worse prognosis for complete facial nerve recovery compared to Bell's palsy — refer to ENT urgently
Incomplete eye closure (lagophthalmos): prescribe artificial tears and tape eye shut at night — corneal exposure keratopathy risk

Contraindications

Hypersensitivity to aciclovir or valaciclovir
Severe dehydration (increases nephrotoxicity risk)

Side effects

Nausea and vomiting
Headache
Nephrotoxicity (crystalluria — especially with dehydration; maintain adequate fluid intake)
Dizziness and confusion (high doses or renal impairment)
Rash
Elevated transaminases

Interactions

Probenecid and cimetidine — reduce renal clearance of aciclovir (increased plasma levels)
Mycophenolate mofetil — additive immunosuppressant considerations
Nephrotoxic drugs — additive renal toxicity risk

Monitoring

Renal function (U&E) during treatment
Facial nerve function (Sunnybrook or House-Brackmann grading)
Hearing and vestibular function

Reference: BNFc; BNF; NICE CKS Shingles; ENT-UK Ramsay Hunt Guidelines; Cochrane Review Zoster. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways