Tricyclic antidepressants reduce PHN pain, but their use is limited by side effects. Opioid medications are not generally recommended for treatment except in specific circumstances. Such cases should involve a pain specialist in patient care due to mixed evidence of efficacy and concerns about potential for abuse and addiction.PHN is the most common long-term complication of herpes zoster. The incidence and prevalence of PHN are uncertain due to varying definitions. Approximately 20% of people affected by herpes zoster report pain in the affected area three months after the initial episode of herpes zoster, and 15% of people similarly report this pain two years after the herpes zoster rash. Since herpes zoster occurs due to reactivation of the varicella zoster virus, which is more likely to occur with a weakened immune system, both herpes zoster and PHN occur more often in the elderly and in people with diabetes mellitus. Risk factors for PHN include older age, a severe herpes-zoster rash, and pain during the herpes zoster episode. PHN is often very painful and can be quite debilitating. Affected individuals often experience a decrease in their quality of life. Signs and symptoms
Symptoms:
With resolution of the herpes zoster eruption, pain that continues for three months or more is defined as postherpetic neuralgia. Pain is variable, from discomfort to very severe, and may be described as burning, stabbing, or gnawing.Signs:
Area of previous herpes zoster may show evidence of cutaneous scarring. Sensation may be altered over the areas involved, in the form of either hypersensitivity or decreased sensation.
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). The anticonvulsant medications pregabalin and gabapentin also effectively relieve postherpetic neuralgia pain. Treatment with pregabalin leads to a reduction in pain intensity of 50% or more in one person out of every 4–5 people treated (NNT=4–5). Similarly, treatment with gabapentin also leads to a 50% reduction in pain intensity in one person out of every 7-8 people treated (NNT=7.5).Opioids such as tramadol, methadone, oxycodone, and morphine have not been well-studied for postherpetic neuralgia treatment. Acetaminophen and nonsteroidal anti-inflammatory drugs are thought to be ineffective and have not undergone rigorous study for PHN. Prognosis
The natural history of postherpetic neuralgia involves slow resolution of the pain syndrome. A subgroup of affected individuals may develop severe, long-lasting pain that does not respond to medical therapy. Epidemiology
In the United States each year approximately 1,000,000 individuals develop herpes zoster. Of those individuals, approximately 10–18% develop postherpetic neuralgia.Fewer than 10 percent of people younger than 60 develop postherpetic neuralgia after a bout of herpes zoster, while about 40 percent of people older than 60 do. References
Further reading
Hempenstall K, Nurmikko TJ, Johnson RW, AHern RP, Rice AS (July 2005). "Analgesic therapy in postherpetic neuralgia: a quantitative systematic review". PLOS Medicine. 2 (7): e164. doi:10.1371/journal.pmed.0020164. PMC 1181872. PMID 16013891. == External links ==