By Pat Anson, Editor

Cymbalta and some other anti-depressants are moderately effective at relieving diabetic nerve pain, according to a new report by the Agency for Healthcare Research and Quality (AHRQ).

But researchers found little or no evidence that opioids, Lyrica, Neurontin and other widely prescribed medications are helpful in treating neuropathy pain.

Nearly 26 million Americans have diabetes and about half have some form of neuropathy, according to the American Diabetes Association. 

Diabetic peripheral neuropathy causes nerves to send out abnormal signals. Patients can feel stinging or burning pain, as well as loss of feeling, in their toes, feet, legs, hands and arms.

"Providing pain relief for neuropathy is crucial to managing this complicated disease," said lead author Julie Waldfogel, PharmD, of The Johns Hopkins Hospital in Baltimore.

"Unfortunately, more research is still needed, as the current treatments have substantial risk of side effects, and few studies have been done on the long-term effects of these drugs."

In a systematic review of over 100 clinical studies published in the journal Neurology, AHRQ researchers found moderate evidence that the SNRI antidepressants duloxetine (Cymbalta) and venlaxine (Effexor) were effective in reducing neuropathic pain. Nausea, dizziness and somnolence were common side effects of the drugs.

The evidence was weaker for anti-seizure medication such as pregabalin (Lyrica) and oxcarbazepine (Trileptal). Common side effects from those drugs are weight gain, dizziness, headache and nausea.

While pregabalin works in the same way as gabapentin (Neurontin) -- both are often used to treat nerve pain -- the reviewers found gabapentin was not more effective than placebo. The seizure drug valproate and capsaicin cream were also found to be ineffective.

Oxycodone was not effective in treating neuropathy pain, and the evidence was weak for two other opioids, tramadol and tapentadol.

The U.S. Food and Drug Administration has approved only three medications -- duloxetine, pregabalin and tapentadol -- for diabetic nerve pain. However, many others drugs are prescribed “off label” for the disease.

"We hope our findings are helpful to doctors and people with diabetes who are searching for the most effective way to control pain from neuropathy," said Waldfogel. "Unfortunately, there was not enough evidence available to determine if these treatments had an impact on quality of life.”

Researchers noted that all of the studies were short-term, many for less than three months, and even the most effective drugs had relatively high rates of side effects. They say longer-term studies are needed so that adverse effects and the continued effectiveness of the drugs can be assessed.