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

How it works

It is converted to aciclovir, which after phosphorylation inhibits viral DNA polymerase and terminates the growing viral DNA chain, halting replication.

Prescribing in practice

• Reduce the dose in renal impairment and maintain adequate hydration, as accumulation can cause reversible neurotoxicity (confusion, agitation, hallucinations).
• Treatment is most effective when started early, ideally within the first days of symptom or rash onset, including in Ramsay Hunt syndrome and Bell's palsy.
• Higher antiviral doses are used for zoster than for simple herpes simplex; check current prescribing references for the indication.

Monitoring

Assess renal function in older patients and those with impairment, and watch for neurological symptoms that may indicate accumulation; ensure good fluid intake.

Counselling the patient

• Start treatment as soon as possible after symptoms begin for the best benefit.
• Drink plenty of fluids while taking it, particularly in older age.
• Report confusion, drowsiness or hallucinations, especially if you have kidney problems.

Evidence & guidelines

Improved oral bioavailability over aciclovir allows less frequent dosing; antivirals started early reduce the severity and duration of herpes zoster and are used adjunctively in facial nerve palsy per UK guidance.