Zoster-associated pain: what is known, who is at risk and how can it be managed?

Herpes zoster episodes commence with a prodromal period of about 4 days with symptoms including pain and malaise. This is followed by a rash lasting approximately 2-4 weeks, with possible subacute herpetic neuralgia for up to 3 months, followed, in some patients, by a period of post-herpetic neuralgia (PHN) lasting months or possibly years. Severe acute pain is more likely in older females and those with a prodrome or severe rash. Two separate mechanisms of PHN have been proposed: the first is that the excitability of primary afferent neurons is increased after nerve damage, causing irritable nociceptors and central sensitization, resulting in pain and allodynia; the second involves the degeneration of nociceptive neurons, which leads to deafferentation with central hyperactivity, causing pain but without allodynia. Both mechanisms may co-exist in an individual patient. Treatments for acute herpes zoster and PHN include established antivirals, alone or in combination with steroids, analgesics and neural blockade with local anaesthetics. Commonly used pain relief includes acetaminophen/paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), opioid analgesics, tricyclic antidepressants, gabapentin, pregabalin and topical analgesics. Effective and long-lasting pain relief in herpes zoster and PHN remains a largely unmet medical need.