Painful diabetic neuropathy underdiagnosed, undertreated

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Painful diabetic neuropathy underdiagnosed, undertreated
April 15, 2007
by Hannah Brown
BNet/Internal Medicine News

GLASGOW, SCOTLAND -- Painful neuropathy is common in people with diabetes, but many patients never receive treatment for the condition, according to Dr. Solomon Tesfaye, Royal Hallamshire Hospital, Sheffield, England.

"The end result is quite a drastic reduction in quality of life," Dr. Tesfaye said at the Diabetes U.K. Annual Professional Conference.

Painful neuropathy is present in approximately 26% of patients with type 2 diabetes, and among those affected, 80% have moderate to severe pain, according to Dr. Tesfaye. Referring to the results of a study done in 350 patients in Liverpool. England, he said that 12.5% of people with pain had never reported their symptoms to a physician, and just under 40% had not received any pain treatment (Diabet. Med. 2004;21:976-82).

Treatments for the condition can either target symptom improvement or alter disease progression. Agents including SSRIs, anticonvulsants, and opioids have been tested for the condition, but only two analgesic drugs are currently approved by the Food and Drug Administration to treat painful diabetic neuropathy--pregabalin and duloxetine--and management remains a challenge, Dr. Tesfaye said.

There have been three clinical trials of each agent during the past few years showing significant improvements in symptoms but also dose-dependent side effects, including sleepiness and dizziness, and for duloxetine alone, nausea. Dr. Tesfaye cautioned that pregabalin had also been associated with edema, so this drug should not be given to patients who already have this condition.

Additional experimental treatments for which more evidence is needed include venlafaxine, which might induce clinically significant EEG abnormalities; [alpha]-lipoic acid, which seems to be efficacious starting at 2 weeks; and combinations of morphine and pregabalin, which seem to be more effective at lower doses than either is at full dose, Dr. Tesfaye said.

"We can only expect 50% pain relief with all the drugs in around one-third of patients, and for many the therapy can be worse than disease." Dr. Tesfaye said. "We need to look at mechanisms of neuropathic pain in more detail. We know it can be instigated by central and peripheral lesions and that these could be early in the disease course."

He suggested that the condition might have CNS effects in addition to peripheral manifestations, underscoring the necessity for greater understanding of the biological causes of this type of pain.