What is Postherpetic Neuralgia

Postherpetic neuralgia is a complication of shingles caused by the same virus that causes chickenpox. Sometimes, particularly in older people, shingles pain persists long after the rash has healed. This condition can be mild or severe - the most severe cases can lead to insomnia, weight loss, depression, and disability.

Postherpetic neuralgia is not directly life-threatening. About a dozen medications in four categories have been shown in clinical trials to provide some pain relief. These include:

Tricyclic antidepressants (TCAs)

TCAs are often the first type of drug given to patients suffering from this condition. The TCA amitryptiline was commonly prescribed in the past, but although effective, it has a high rate of side effects. Desipramine and nortriptyline have fewer side effects and are therefore better choices for older adults, the most likely group to have postherpetic neuralgia.

Common side effects of TCAs include dry eyes and mouth, constipation, and grogginess. People with heart arrhythmias, previous heart attacks, or narrow angle glaucoma should usually use a different class of drugs.

Anticonvulsants

Some drugs that reduce seizures can also treat this condition because seizures and pain both involve abnormally increased firing of nerve cells. An antiseizure medication, carbamazepine, is effective for postherpetic neuralgia but has rare, potentially dangerous side effects so a newer anticonvulsant, gabapentin, is far more often prescribed. Side effects of the drug include drowsiness or confusion, dizziness, and sometimes ankle swelling.

Opioids

Opioids are strong pain medications used for all types of pain. They include oxycodone, morphine, tramadol, and methadone. Opioids can have side effects - including drowsiness, mental dulling, and constipation - and can be addictive, so their use must be monitored carefully in those with a history of addiction.

Topical local anesthetics

Local anesthetics applied directly to the skin of the painful area affected by this condition are also effective. Lidocaine, the most commonly prescribed, is available in cream, gel, or spray form. It is also available in a patch that has been approved by the Food and Drug Administration for use specifically in postherpetic neuralgia.

With topical local anesthetics, the drug stays in the skin and therefore does not cause problems such as drowsiness or constipation. Capsaicin cream may be somewhat effective and is available over the counter, but most people find that it causes severe burning pain during application.

Postherpetic itch

The itch that sometimes occurs during or after shingles can be quite severe and painful. Clinical experience suggests that postherpetic itch is harder to treat than postherpetic neuralgia. Topical local anesthetics (which numb the skin) provide substantial relief to some patients. Since postherpetic itch typically develops in skin that has severe sensory loss, it is particularly important to avoid scratching. Scratching numb skin too long or too hard can cause injury.