An in-depth report on the causes, diagnosis, treatment, and prevention of shingles and chickenpox.
Chicken pox; Herpes zoster; Postherpatic neuralgia
Postherpetic neuralgia (PHN) is difficult to treat. Once PHN develops, a patient may need a multidisciplinary approach that involves a pain specialist, psychiatrist, primary care physician, and other health care providers.
The American Academy of Neurology (AAN) treatment guidelines for postherpetic neuralgia recommend:
Topical Pain Relievers. Creams, patches, or gels containing various substances can provide some pain relief.
Skin Coolants. Ethyl chloride (Chloroethane) and fluori-methane are chemicals that cool the blood vessels in the skin. Sprays that contain these chemicals are not anesthetics, but they are used to inactivate the sensitive areas. To use the spray, the patient must be in a comfortable position. The spray bottle is held upside-down, about 12 - 18 inches from the targeted area. The face must be covered if the spray is being used near the head.
Tricyclic antidepressants relieve pain in up to two-thirds of patients. These drugs not only relieve depression, which can be common in PHN sufferers, but certain tricyclics specifically block sodium channels, which play a role in causing pain in PHN. Nortriptyline (Pamelor, Aventyl), amitriptyline (Elavil, Endep), and desipramine (Norpramin) are standard drugs.
They may be more effective when started during the first year after symptoms begin. It may take several weeks for the drugs to become fully effective. They do not work as well in patients who have burning pain or allodynia (pain that occurs with normally non-painful stimulus, such as a light touch or wind).
Unfortunately, tricyclics have side effects that are particularly severe in the elderly, who are also more likely to have PHN. Desipramine and nortriptyline have fewer side effects than amitriptyline and are preferred for older patients. Side effects include dry mouth, blurred vision, constipation, dizziness, difficulty urinating, disturbances in heart rhythms, and an abrupt drop in blood pressure when standing up.
Certain anticonvulsant drugs have effects that block over-excitation of nerve cells and may be helpful for PHN patient. (Anticonvulsant drugs are also known as anti-seizure drugs.)
Gabapentin. Gabapentin (Neurontin) was the first anticonvulsant drug approved for PHN. Studies suggest significant pain relief in patients with PHN and reduction in the use of opioids. Many patients also report improved quality of life, including better sleep. Gabapentin is also showing promise in combination with valacyclovir for reducing pain from an acute herpes zoster attack.
Side effects include skin rashes, mood swings or thoughts of suicide, headache, dizziness, sleepiness, swelling, and upset stomach. Some people have visual disturbances, ringing in the ears, agitation, or odd movements when drug levels are at their peak. These side effects may limit their value in older people who are at risk of falling. In general, however gabapentin is safer than tricyclic antidepressants for elderly patients.
Pregabalin. Pregabalin (Lyrica) is similar to gabapentin. Like gabapentin, side effects can include sleepiness and dizziness
Other Anticonvulsant Drugs. The AAN guidelines found insufficient evidence to recommend carbamazepine (Tegretol).
Opioids. Patients with severe pain that does not respond to tricyclic antidepressants may need powerful painkilling opioid drugs. They may be taken by mouth or delivered through a skin patch. Oxycodone is the standard opioid for PHN. Morphine is also used. Methadone (Dolophine) may also be helpful. Constipation, drowsiness, and dry mouth are common side effects of opioids.
Tramadol. Tramadol (Ultram) is a pain reliever that has been used as an alternative to opioids. It has opioid-like properties but is not as addictive. (Dependence and abuse have been reported, however.) It can cause nausea but not severe gastrointestinal problems, as NSAIDs can. Studies suggest it might be very helpful for PHN patients, particularly those with heart problems or other conditions that restrict tricyclic antidepressants.
Antiviral Drugs. Researchers are investigating whether treatment with antiviral drugs may help reduce the pain associated with postherpetic neuralgia.
Surgery. Certain surgical techniques in the brain or spinal cord attempt to block nerve centers associated with postherpetic neuralgia. These methods carry risk for permanent damage, however, and should be used only as a last resort when all other methods have failed and the pain is intolerable. Most studies indicate that surgery does not relieve PHN pain.
Stress Reduction Techniques. A number of relaxation and stress-reduction techniques may be helpful for managing chronic pain. They include meditation, deep breathing exercises, biofeedback, and muscle relaxation. These techniques may apply to patients with severe pain from acute infection or persistent long-term postherpetic neuralgia. [For more information, see In-Depth Report #31: Stress.]
Behavioral Cognitive Therapy. Behavioral cognitive therapy is showing benefit in enhancing patients' beliefs in their own abilities for dealing with pain. Using specific tasks and self-observation, patients gradually shift their fixed ideas that they are helpless against the pain that dominates their lives to the perception that it is a manageable experience. The skill of the therapist is very important to its success.
Many people with chronic pain such as PHN turn to alternative treatments for relief. Aside from hypnosis, little evidence indicates that these treatments work for PHN. Acupuncture is one such unproven remedy.
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