A Pooled Analysis of Three Clinical Studies

Three Clinical StudiesINTRODUCTION

Pain is one of the most common reasons why patients seek health care. Estimates indicate that 20% of the elderly in the general population and 50% of community-dwelling older adults have some form of persistent pain. Approximately 20% of older people take analgesics several times a week for pain relief.

One source of pain is herpes zoster infection, also called shingles. The primary infection (chickenpox) usually occurs in childhood; afterward, it remains latent in the cranial nerve and dorsal root ganglia for the patient’s lifetime. When the virus is active, it produces characteristic vesicular skin rashes that follow the underlying route of the inflamed nerves to produce shingles. Reactivation of the virus is exacerbated by increasing age or immunosuppression of the infected person. More than one million cases of herpes zoster arise each year, and from 10% to as many as 34% of afflicted individuals develop painful neuralgia, known as postherpetic neuralgia (PHN).
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PHN is defined as pain in the area affected by herpes zoster that persists for at least three months after crusting of the herpes zoster rash. It is characterized by intermittent pain with a sharp, lancinating, or jabbing sensation; constant deep, burning pain; or pain provoked by trivial stimuli and altered sensation that may continue long after the rash has healed. The incidence of PHN rises dramatically with age; nearly 50% of patients over the age of 60 experience enduring neuropathic pain.

Chronic pain is associated with a diminished quality of life. Undertreatment of pain is a major health problem and may be a causal factor for depression, social isolation, sleep disturbance, and impaired ambulation. Because of the high emotional and psychological toll of chronic pain, it is essential that clinicians evaluate the impact of pain and pain treatment on a patient’s overall health status when assessing treatment outcome and the progress of PHN. These notions are substantiated by the recent work of Oster and colleagues, who surveyed patients with PHN and found that they experience substantial pain as well as significant dysfunction as a result of PHN, as measured by a decline in general activity, mood, relations with other people, sleep, and enjoyment of life.

Pharmacotherapy is the mainstay of chronic pain management. Therapies for PHN may include opioid and non-opioid analgesics, tricyclic antidepressants (TCAs), topical lidocaine, and certain anticonvulsants. Gabapentin (Neurontin drug), an anticonvulsant, is one of the newer drugs approved for the treatment of PHN. Major studies have reported the efficacy of gabapentin in the treatment of neuropathic pain in PHN and in various neuropathic pain syndromes.

In one pivotal study of PHN, by Rowbotham et al., gaba-pentin significantly improved vitality, bodily pain, and mental health on the 36-item Short Form Survey (SF-36). In a second key study, by Rice and Maton, patients receiving for PHN showed similar improvements in six of eight SF-36 domains. The large sample size of this study contributes to the sensitivity of our present findings.

This article summarizes the effects of gabapentin and placebo on patient-reported outcome domains captured in the SF-36 in patients with PHN by the use of a pooled analysis. This pooled analysis includes all PHN patients from the two pivotal studies as well as all PHN patients from an efficacy study of gabapentin canadian in various neuropathic pain syndromes.

Category: Health

Tags: Clinical Studies, Pooled Analysis

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