TOWARDS AN ALGORITHM FOR MANAGEMENT OF PHN

*R.W. Johnson & U. Johnson. Zoster Unit, Pain Management Clinic, Bristol Royal Infirmary & University of Bristol, England.

Application of evidence-based therapy for PHN is hampered partly by apaucity of satisfactory studies and partly because there are a number of clinicallydistinct sub-types of the condition to which the generic term PHN is attached. Growing knowledge of the pathophysiology of PHN and developmentof drugs with targeted sites of action may facilitate improved outcome.
Like all chronic pain conditions, there are psycho-social and
environmental factors involved in PHN aetiology and persistence: therapy aimed solely at the physical pathology may be sub-optimal.
In formulating a plan for therapy, it is necessary to classify the
condition. The principal sub-types may be identified by simple history and clinical examination with no more sophisticated diagnostic aids than a pin, cotton wool, a warm finger and a piece of cold steel or glass.
Contending treatments must be assessed for efficacy, risk and cost. Lack of evidence of efficacy does not equate with evidence of lack of efficacy - a number of well designed relevant studies have yet to be undertaken. An
algorithm classified according to strength of evidence, cost and safety will be proposed with invitation to comment and develop the scheme by internet communication. The algorithm will include physical, topical and systemic pharmacological therapies as well as nerve block treatments and will propose development of a cognitive - behavioural pain management programme suitable
for elderly patients with PHN.
Optimal use of existing tools may improve outcome. Advances in understanding of factors associated with PHN and development of new drugs may further improve the situation. Prediction during the acute attack of HZ of those most at risk of developing PHN permits appropriate use of preventive measures such as antiviral drugs. It may be that early use of certain tricyclics e.g. amitriptyline, or anticonvulsants e.g. gabapentin, may offer protection. The place of sympathetic and somatic nerve blocks remains controversial. Vaccination may reduce the incidence of zoster and/or alter its propensity to cause PHN.

Corresponding Author: R.W. Johnson, MB.,BS.,FRCA. Consultant Anaesthetist, Zoster Unit, Pain Management Clinic, Bristol Royal Infirmary, Bristol BS2 8HW, United Kingdom; E-mail: RWJBRISTOL@AOL.COM