PHN is defined as pain in a dermatomal distribution that lasts for at least 90 days after an outbreak of herpes zoster.

[2] Postherpetic neuralgia is the most common long-term complication of herpes zoster, and occurs in approximately 20% of patients with shingles.

Such cases should involve a pain specialist in patient care due to mixed evidence of efficacy and concerns about potential for abuse and addiction.

The damage causes nerves in the affected dermatomic area of the skin to send abnormal electrical signals to the brain.

[5] A key factor in the neural plasticity underlying neuropathic pain is altered gene expression in sensory dorsal root ganglia neurons.

These changes contribute to increased NMDA glutamate receptor-dependent excitability of spinal dorsal horn neurons and are restricted to the ipsilateral (injured) side.

[6] The varicella vaccine is approved for infants to prevent chickenpox, which also protects against PHN from a herpes zoster infection.

[4] A 2013 Cochrane meta-analysis of 6 randomized controlled trials (RCTs) investigating oral antiviral medications given within 72 hours after the onset of herpes zoster rash in immunocompetent people for preventing postherpetic neuralgia (PHN) found no significant difference between placebo and aciclovir.

Additionally, there was no significant difference in preventing the incidence of PHN found in the one RCT included in the meta-analysis that compared placebo to oral famciclovir treatment within 72 hours of HZ rash onset.

[2] Lidocaine patches (5% concentration) are approved in the United States and Europe to treat PHN though evidence supporting their use is limited.

[8] Low-dose capsaicin may be useful for reducing PHN-associated pain but is limited by side effects (redness and a burning or stinging sensation with application) and the need to apply it four times daily.

[2] For every eleven people treated with a high-dose capsaicin patch for up to 12 weeks, one person experienced a significant improvement in their pain.

[9] Due to the need for topical anesthesia before application of the high-dose capsaicin patch, referral to a pain specialist is generally recommended if this approach is being considered.

[2] Additionally, of every sixteen people treated with a TCA, one person is expected to stop the medication due to a bothersome side effect, such as dry mouth, constipation, or urinary retention (number needed to harm=16).

Between 2016 and 2023, 18 clinical trials have been carried out evaluating 15 molecules with pharmacological actions on nine different molecular targets: antagonism of the angiotensin type 2 receptor (AT2R) (olodanrigan), inhibition of the α2δ subunit of the voltage-gated calcium channel (VGCC)(crisugabalin, mirogabalin and pregabalin), activated sodium channel (VGSC) blockade (funapide and lidocaine), cyclooxygenase-1 (COX-1) inhibition (TRK-700), adapter-associated kinase 1 inhibition ( AAK1) (LX9211), lanthionine synthase C-like protein (LANCL) activation (LAT8881), N-methyl-D-aspartate (NMDA) receptor antagonism (esketamine), mu opioid receptor agonism (tramadol, oxycodone e hydromorphone) and nerve growth factor (NGF) inhibition (fulranumab).

A subgroup of affected individuals may develop severe, long-lasting pain that does not respond to medical therapy.