Medical Health Encyclopedia

Gabapentin. Gabapentin (Neurontin) is the most effective of these to date and is the first oral agent approved for PHN. Studies are reporting 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. (It is also showing promise in combination with valacyclovir for reducing pain from an acute herpes zoster attack.)

Side effects include skin rashes, increased risk for infection, headache, dizziness, sleepiness, swelling, and upset stomach. Some people experience 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 the tricyclics for this group.

Other Anti-Seizures Agents.Pregabalin (Lyrica) is an anti-seizure agent that has actions similar to gabapentin. Several clinical trials have reported that it is effective in reducing pain and improving sleep. However, like gabapentin, side effects can include sleepiness and dizziness. Based on current evidence, the American Academy of Neurology (AAN) has recommended pregabalin as an effective treatment for PHN. The drug was approved by the FDA at the end of 2004 and will be available in the United States in 2005. The AAN guidelines found insufficient evidence to recommend the anti-seizure medication carbamazepine (Tegretol).

Opioids and Opioid-like Agents

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Opioids. Powerful pain-killing opioid drugs may be needed in patients with severe pain that does not respond to tricyclic antidepressants. They may be delivered orally or using a patch. Oxycodone is the standard opioid for PHN. Methadone (Dolophine) may also be helpful. In one 2002 study of elderly patients, opioids were more effective than tricyclics and had fewer side effects. Although there is some concern that drug dependency may develop, studies indicate that if these narcotics are carefully monitored, they remain effective and the risk for addiction is very low. Side effects include nausea, sleepiness, and constipation.