Postherpetic neuralgia: New hopes in prevention with adult vaccination and in treatment with a concentrated capsaicin patch
Authors: Gawecka Ewa , Viken Oddbjørn 
Published: October 2012

Abstract

Background and purpose
Postherpetic neuralgia (PHN) is a complication of acute herpes zoster (HZ). The evidence base for management of PHN has increased by recent publications. Therefore, we reviewed incidence of HZ, prevalence, risk factors, and mechanism of PHN pain, prevention and treatment of PHN with special interest in studies on adult vaccination and topical application of lidocaine and concentrated capsaicin patch.

Methods
We searched databases with an English language restriction: MEDLINE 1944–2011, EMBASE 1988–2011, PubMed, and the Cochrane Controlled Trial Register and Cochrane Library (2011). From retrieved publications, we selected studies focusing on our main goals, prevention and treatment of PHN in particular. The review was therefore systematic, but with a pragmatic approach to which studies to select for closer review.

Results
From the large number of abstracts retrieved we selected 65 papers for closer review and as evidence base for our conclusions and recommendations for prevention and treatment of HZ and PHN. The incidence of HZ and risks of having PHN after HZ increases markedly with age above 60–70. Severity of symptoms and their impact on quality of life is a major health problem of persons above 70 years of age. Adult vaccination with the reinforced varicella virus vaccine reduces the incidence of HZ and PHN by about 50%. This is an important health and quality of life gain for the elderly. Antiviral drugs given early in an episode of HZ reduce pain and duration of HZ and decrease the risk of PHN.
Pharmacological management of PHN are with nortriptyline (or amitriptyline in the younger patients), and or a gabapentinoid as first line drugs. Early treatment also is with topical lidocaine for immediate but short-lasting relief of burning hyperalgesia, and topical capsaicin relieving hypersensitivity for up to 12 weeks. A number of second and third line drugs have less evidence-base for effect, and often more adverse effects than the first line drugs: serotonin and noradrenaline uptake inhibitors (venlafaxin, duloxetin), antiepileptics (valproate), and opioid analgesics. Opioids are indicated for bridging in patients with severe PHN-symptoms while waiting for the more specific first line drugs to take effect. In these elderly patients, systemic pharmacological treatments are always a difficult balance between effects and adverse effects. It is important with close supervision of the patients, especially during start-up of systemically administered drugs, in order to prevent tragic complications from falls in sedated, dizzy, and confused elderly patients. Topical treatment with lidocaine and capsaicin patches does not have these problems.

Conclusions
Prevention of this significant health problem of the increasing elderly population is now possible through adult vaccination against varicella zoster virus (VZV) reactivation, as well as vigorous and early antiviral treatment during acute HZ. The evidence -base supports the oral use of tricyclic antidepressants, gabapentinoids, and opioids for bridging till the first line drugs take effect. Topical therapy with lidocaine and capsaicin patches is effective and well supported by evidence. A number of second and third line drugs and treatments are available, but have less evidence-base. All drug treatments, except topical lidocaine and capsaicin, have adverse effects that are often problematic and can be dangerous in the elderly patients. Close supervision of the patients is mandatory.

Implications
Recent advances in prevention and management of this serious health problem should be better known and implicated: Adult vaccination for prevention of varicella zoster virus reactivation, antiviral drugs and combinations of drugs can reduce the suffering from acute HZ and chronic PHN. Topical lidocaine and capsaicin are now evidence-based therapies that reduce suffering from hypersensitivity and hyperalgesia in patients with PHN. When properly applied, they have few complications.