Authors: Mark W. Douglas¹; Robert W. Johnson²; Anthony L. Cunningham¹

Source: Drug Safety, Volume 27, Number 15, 2004 , pp. 1217-1233(17)

Publisher: Adis International

Abstract:

Herpes zoster occurs in up to 20% of people infected with varicella-zoster virus, due to reactivation of the virus from latently infected sensory ganglia. Although pain is a typical feature of acute zoster, pain persisting for more than a month after resolution of the rash is less common and is termed postherpetic neuralgia (PHN). The pain associated with PHN is neuropathic in origin and is notoriously difficult to treat. The incidence of herpes zoster and its associated complications both increase with age, so PHN should be seen more commonly in an aging population.

Vaccination with live, attenuated varicella vaccine is safe and efficacious, particularly in children. It decreases the incidence of acute varicella and subsequent herpes zoster. Aciclovir is well tolerated, with renal toxicity only at high intravenous doses. Treatment of acute varicella with aciclovir attenuates acute illness but does not prevent herpes zoster. Treatment of herpes zoster with aciclovir or its derivatives minimises symptoms and may reduce the rate of PHN. Foscarnet is an alternative for an aciclovir-resistant virus but its use is limited by renal and CNS toxicity. Corticosteroids reduce acute pain in herpes zoster but do not affect the incidence of PHN. Their use in some patients may be limited by adverse effects such as gastritis and impaired glucose tolerance.

Treatment of established PHN is difficult and may require a holistic approach. Tricyclic antidepressants and gabapentin are the systemic agents with the most proven benefit, although opioids such as oxycodone and NMDA receptor antagonists such as ketamine may be useful in some people. Adverse effects from tricyclic antidepressants are common but usually mild, while gabapentin is generally well tolerated. Although effective, the relatively common adverse effects of opioids and ketamine limit their usefulness in treating PHN. Topical treatment with 5% lidocaine patch or capsaicin is of benefit in some patients and is generally well tolerated. Intrathecal methyl prednisolone may be considered for intractable pain but efficacy and safety have not been confirmed.

Keywords: Antivirals, adverse reactions; Postherpetic neuralgia; Corticosteroids, therapeutic use; Varicella zoster virus vaccine, therapeutic use; Tricyclic antidepressants, therapeutic use; Antiepileptic drugs, adverse reactions; Antivirals, therapeutic use; Corticosteroids, adverse reactions; Varicella zoster virus vaccine, adverse reactions; Tricyclic antidepressants, adverse reactions; Antiepileptic drugs, therapeutic use; Lidocaine, adverse reactions; Lidocaine, therapeutic use; Capsaicin, therapeutic use; Capsaicin, adverse reactions; Opioids, adverse reactions; Opioids, therapeutic use; NMDA antagonists, therapeutic use; NMDA antagonists, adverse reactions; Local anaesthetics, therapeutic use; Adverse drug reactions; Benefit risk assessment; Local anaesthetics, adverse reactions

Document Type: Review article

Affiliations: 1: 1 Centre for Virus Research, Westmead Millennium Institute, Westmead Hospital and University of Sydney, Westmead, Australia 2: 2 Department of Anaesthetics, University of Bristol and Bristol Royal Infirmary, Bristol, UK

Publication date: 2004-01-01

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