DEAR MAYO CLINIC: How do you treat chronic postherpetic neuralgia?
ANSWER: Postherpetic neuralgia is a painful condition that affects the nerve fibers and skin. It can be difficult to treat. Effective therapy often requires a combination of several medications.
Postherpetic neuralgia is a complication of shingles - a reactivation of the varicella-zoster virus, which initially causes chickenpox. After an infection of chickenpox, the varicella-zoster virus remains in a person's body, lying dormant inside nerve cells. Years later, the virus may reactivate and cause shingles. Once reactivated, the virus travels along nerve fibers, causing pain. When the virus reaches the skin, it produces a rash and blisters.
A case of shingles usually heals within a month. But some people continue to feel pain long after the rash and blisters disappear. That pain is postherpetic neuralgia. It's caused by damage to the sensory nerves affected by the varicella-zoster virus. Symptoms may include sharp and jabbing, burning, or deep and aching pain; extreme sensitivity to touch and temperature change; and itching and numbness in the area affected by shingles.
Typically, postherpetic neuralgia gradually disappears during the first three months following a bout of shingles. For about 10 to 20 percent of people the pain may persist for a year or more. The risk of postherpetic neuralgia following shingles increases with age.
There's a vaccine that can decrease the risk of shingles and postherpetic neuralgia. If you're 60 or older, ask your doctor about getting this vaccine. Another prevention step is treat shingles with medicine as soon as it starts. If you notice a new, severe pain in a narrow band on one side of your body, see your doctor right away. The pain of shingles often precedes the appearance of the rash. Antiviral therapy during this early stage can help prevent postherpetic neuralgia.
Unfortunately, no one treatment reliably relieves the pain of postherpetic neuralgia. Instead, treatment usually involves several medications. Drugs that can be effective include topical agents, antidepressants, anticonvulsives and opioids. As we move through the list, the frequency and severity of side effects generally increases, so doctors usually start with the first options and gradually add others only if needed.
A variety of topical medications may be used to treat postherpetic neuralgia. Skin patches containing lidocaine or capsaicin are the most common. Lidocaine is a prescription pain reliever that numbs the skin. Capsaicin is a compound found in chili peppers that can help relieve pain. Capsaicin causes a burning sensation when it's first used, and it may take up to four weeks for substantial pain relief to occur with capsaicin.
Antidepressants can be used to treat postherpetic neuralgia even in patients who aren't depressed. These drugs, such as nortriptyline or duloxetine, affect key brain chemicals, including serotonin and norepinephrine, which play a role in how the body interprets pain. Medications for treatment of seizures (anticonvulsives such as gabapentin or pregabalin) also may lessen the pain associated with postherpetic neuralgia. These medications stabilize abnormal electrical activity in the nervous system caused by injured nerves. Opioids - powerful painkilling medications such as oxycodone or morphine - can help manage postherpetic neuralgia, as well.
It may take several attempts at combining medications before a patient gets relief from postherpetic neuralgia. If, after trying several alternatives, treatment with medications fails to reduce pain, an evaluation with a physician who specializes in pain medicine should be the next step.
Depending on a patient's pain and other medical conditions, a pain specialist may be able to offer additional therapies, such as more powerful medications, injections or possibly the use of electrical stimulation of the damaged nerves. Alleviating postherpetic neuralgia completely is sometimes challenging. If pain continues despite treatment, take hope in the knowledge that postherpetic neuralgia remains an active area of research for new drugs and therapy. - David Martin, M.D., Ph.D., Anesthesiology, Mayo Clinic, Rochester, Minn.
(Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care. E-mail a question to firstname.lastname@example.org , or write: Medical Edge from Mayo Clinic, c/o TMS, 2225 Kenmore Ave., Suite 114, Buffalo, N.Y., 14207. For more information, visit www.mayoclinic.org.)