Post-Herpetic Neuralgia Chronic Pain Management!

The condition of persistent pain in the body, where an outbreak of the Varicella Zoster virus has caused Shingles, is termed as post-herpetic neuralgia. It is a debilitating complication of the herpes zoster virus. The blisters that occur in shingles develop a crust formation and neuralgia begins after these crusts are formed. It may also occur in people who do not produce the crustaceous lesions. A burning pain that is long-lasting, even after the rash and the blisters disappear, is observed. There is a criteria of the pain to be persistent for around three months for the confirmation of post herpetic neuralgia.

The cause of this condition is damage of the sensory nerves that can occur due to the movement of the reactivated Herpes Zoster virus from the nerves to the skin. In an individual affected with chickenpox, the infection can involve dorsal root ganglia, where the virus lies dormant. Under conditions like stress due to infection or in an immuno-compromised individual, after a period of time, reactivation of the virus takes place. This reactivation causes production of Shingles on the body. The dormant virus reaches the skin and reactivates to produce lesions.

With an increase in age, the chances of developing post-herpetic neuralgia also increase. It primarily affects older individuals in the age group of 60 to 70 years. Treatment is aimed at pain management and providing symptomatic relief, with improvement of the neuralgia over a period of time. Symptoms of this condition are limited to the area of shingles’ outbreak. Trunk is commonly affected on a unilateral site. It can also occur on face. Common symptoms include pain lasting 3 months or longer after healing of the shingles rash, allodynia, numbness over the affected area and itching. Even a slight touch of cloth over the affected area can cause alleviated pain to the individual. Disturbed sleep and development of clinical depression is usually associated with post herpetic neuralgia. The medications given for post herpetic neuralgia are aimed at pain relief and resolving of symptoms. Management of chronic pain can be brought about by the use of a combination of pain relieving drug classes.

Some commonly used drugs for treatment of post-herpetic neuralgia are as follows:

1. Topical Agents: Numerous topical agents have been effectively used in the treatment of post-herpetic neuralgia. In patients with allodynia or an alleviated pain sensation, topical lidocaine patches are very effective. The nociceptive activity of small nerve fibers is decreased by use of Lidocaine. Also, the brush of clothing is avoided by the patch serving as a protective barrier itself. Another topical agent that has proved effective in pain relief is Capsaicin. Its clinical use is limited due to the burning sensation caused by its application. With regular use, however, the burning sensation gradually reduces. Capsaicin should be used for a minimum period of a month to aid pain relief. Low systemic absorption of the topical agents ensure few side effects caused by them.
2. Antidepressants: The standard drug therapy for treatment of post-herpetic neuralgia include the use of antidepressant drugs. Drugs like Nortriptyline, Amitriptyline are the most commonly used drugs amongst the tricyclic antidepressants for pain relief in post-herpetic neuralgia. These drugs are however associated with various adverse effects like sedation and cardiac dysrhythmias. Other drug classes like Serotonin reuptake inhibitors are used in individuals with low tolerance to the tricyclic antidepressants. Depression symptoms are relieved by the use of this drug class. Specific relief of the chronic pain of post-herpetic neuralgia is not achieved much efficiently though.
3. Anticonvulsants: Neuropathic pain can be relieved by many anticonvulsant drugs. Drugs like Pregabalin have lesser side effects and also require a lesser monitoring than previously used anticonvulsant drugs like Carbamazepine.
4. Opioids: Long term use of opioids shows significant risks like sedation and mental clouding. These drugs are considered safe for use without causing cardiac or hepatic adverse effects. When opioids are prescribed, stool softeners and laxatives should also be given to avoid constipation. Other pain management protocol includes cryotherapy, ablation of the affected roots of nerve, anterolateral cordotomy and even the use of electrical nerve stimulation. The physician should evaluate the best suitable pain management option and provide treatment accordingly.

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