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Antiviral (Prodrug of Aciclovir) Pregnancy: Caution — limited data; aciclovir registry shows no excess malformations; used when VZV infection risk outweighs drug risk

Valaciclovir (ENT — Ramsay Hunt / Bell's Palsy)

Brand names: Valtrex

Adult dose

Dose: Ramsay Hunt: 1000 mg three times daily for 7-14 days; Bell's palsy (herpetic suspected): 500-1000 mg twice daily for 5-7 days (with prednisolone)
Route: Oral
Frequency: Two to three times daily
Max: 3000 mg/day
Valaciclovir is the prodrug of aciclovir with better oral bioavailability (~55% vs ~15%); for Ramsay Hunt syndrome, combine with prednisolone 1 mg/kg/day; start within 72 hours of onset for maximal benefit

Paediatric dose

Dose: Not routinely recommended for Bell's palsy in children N/A/kg
Route: N/A
Frequency: N/A
Max: N/A
Paediatric Ramsay Hunt: specialist advice required; aciclovir IV may be preferred in severe cases

Dose adjustments

Renal

CrCl 15-30 mL/min: 1000 mg twice daily; CrCl <15 mL/min: 500 mg twice daily; haemodialysis: 500 mg once daily

Hepatic

No dose adjustment required for mild-moderate impairment

Paediatric weight-based calculator

Paediatric Ramsay Hunt: specialist advice required; aciclovir IV may be preferred in severe cases

Clinical pearls

  • Ramsay Hunt syndrome: varicella-zoster virus (VZV) reactivation in geniculate ganglion — presents with ear pain, vesicles in ear canal/auricle/palate (zoster auricularis), ipsilateral facial palsy, sensorineural hearing loss, and vertigo; prognosis worse than Bell's palsy (complete recovery in only 10-20% without treatment)
  • Evidence base: prednisolone + valaciclovir combination superior to prednisolone alone in Ramsay Hunt (Murakami et al. Ann Neurol 1997); treat immediately — ideally within 72h; recovery plateaus at 6 months
  • Bell's palsy antivirals: NICE CG186 (2012) does not recommend routine antivirals for Bell's palsy (Engström NEJM 2008 showed no benefit of valaciclovir alone); however, combination prednisolone + valaciclovir may offer marginal benefit in severe cases — practice varies by centre
  • Eye care mandatory in both conditions: lagophthalmos (incomplete eye closure) due to facial nerve palsy risks corneal exposure keratitis — lubricating drops, eye tape at night, gold weight implant if prolonged; ophthalmology referral if corneal involvement
  • Early diagnosis of Ramsay Hunt vs Bell's palsy is critical — look for vesicles inside the ear canal (posterior wall), on the auricle, or palate; VZV serology or PCR from vesicle swab confirms diagnosis

Contraindications

  • Known hypersensitivity to valaciclovir or aciclovir

Side effects

  • Nausea
  • Headache
  • Dizziness
  • Renal impairment (high doses — maintain hydration)
  • Thrombotic thrombocytopenic purpura (TTP) at very high doses in immunocompromised

Interactions

  • Nephrotoxic drugs — additive renal risk
  • Probenecid/cimetidine — reduce renal clearance of aciclovir; monitor in renal impairment

Monitoring

  • Facial nerve recovery (House-Brackmann scale at each visit)
  • Vesicle healing
  • Audiology (sensorineural hearing loss component)
  • Corneal examination (eye care)
  • Renal function (high doses)

Reference: BNFc; BNF 90; Murakami et al. Ann Neurol 1997 (Ramsay Hunt); Engström et al. NEJM 2008 (Bell's palsy); NICE CG186; AAO-HNS Bell's Palsy Guidelines (2013); SIGN 120. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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