Antivirals for Shingles: Aciclovir & Valaciclovir

What antivirals do and do not do, who needs them, the UK regimens, why the shingles dose is so much higher than the herpes dose, and why pain relief is the other half.

Part of the Complete Shingles Guide.

What antivirals do for shingles

Aciclovir, valaciclovir and famciclovir stop varicella zoster from replicating. They do not remove the virus from the body — nothing does — and they do not act as painkillers. What they do, started early, is shorten the time new blisters keep appearing, speed healing, reduce the severity of the acute illness, and reduce the risk of pain persisting after the rash has gone.

That last point is the one worth holding onto. Postherpetic neuralgia is the complication that changes people’s quality of life for months, and early antiviral treatment is one of the few things that influences its likelihood.

Who needs antiviral treatment

Not every case is treated with antivirals, and UK practice weighs age, site and severity. Treatment is generally recommended if you:

• Are over 50, where the risk of prolonged nerve pain is higher
• Have moderate or severe pain, or a moderate or severe rash
• Have a rash anywhere other than the trunk — face, eye, ear, neck, limbs or genitals
• Have a weakened immune system from illness or medication
• Are pregnant or breastfeeding — needs urgent clinical advice rather than self-treatment
• Have eye or ear involvement, or facial weakness, both of which are urgent

Younger adults with mild truncal shingles and little pain may reasonably be managed with pain relief and self-care alone. A pharmacist or prescriber can make that call with you.

The regimens

Aciclovir or valaciclovir?

Both work. The practical difference is dosing frequency against cost. Aciclovir is cheaper but needs five doses a day for a week, spaced through waking hours, and adherence over seven days is where it falls down. Valaciclovir is three times daily, which most people find considerably easier, at a higher price.

If you know you struggle with frequent dosing — or you are unwell, in pain and unlikely to manage a five-times-daily schedule reliably — that is a legitimate reason to discuss valaciclovir rather than a luxury.

Safety, side effects and fluids

Both are well tolerated. Nausea, headache, diarrhoea, abdominal discomfort and dizziness are the common side effects and affect a minority of people. Serious effects are uncommon.

• Drink plenty of fluids throughout the course — both drugs are cleared by the kidneys
• Reduced kidney function needs a lower dose; tell the prescriber if you have kidney problems or are older
• Confusion or agitation is an uncommon effect seen mainly with high doses, dehydration or kidney impairment — seek advice rather than continuing
• Tell the prescriber everything you take, including over-the-counter medicines
• Finish the course even as the rash improves — seven days is the standard length

Antivirals are only half the treatment

Shingles pain is nerve pain, and ordinary painkillers often only partly touch it. Paracetamol, with or without ibuprofen, is the starting point, but where pain is significant, medicines that act on nerve pain — amitriptyline, gabapentin, pregabalin or duloxetine — are used, sometimes alongside the antiviral.

Treating pain properly during the acute phase is not just about comfort: severe early pain is associated with a higher chance of pain persisting, so it is worth saying clearly how bad it is rather than underplaying it. Postherpetic neuralgia covers what happens if pain outlasts the rash.

The full condition picture, including complications and vaccine eligibility, is on our shingles page, and the day-by-day course is in shingles stages.