A study reveals the drug duloxetine is useful in treating diabetes-related pain, but it may worsen control of blood sugar levels. Diabetes is the number one cause of damage to the peripheral nerves in the United States. Neuropathy will first appear as burning or stinging in the feet, usually worse at night. The nerves to the feet are affected first because the damage is occurring along the entire length of the axons and the axons to the feet are the longest in the body.

Duloxetine is one of only two drugs approved for the treatment of diabetic peripheral neuropathic pain (DPNP), a common problem in diabetic patients, Cymbalta® or duloxetine is the first drug approved by the FDA for painful diabetic polyneuropathy. The drug was previously approved as an antidepressant. The drug is an SSNRI meaning it is both a selective serotonin reuptake inhibitor and a selective norepinephrine reuptake inhibitor. By blocking the reuptake of serotonin and norepinephrine, these neurotransmitters increase in the spinal cord and brain. It is speculated that both increased serotonin levels and norepinephrine levels produce an inhibitory effect on the ascending sensory tracts.

Data was collected from three clinical trials to investigate changes in weight, sugar levels, and cholesterol levels in patients with DPNP treated with duloxetine. Short-term treatment with duloxetine was associated with a modest increase in fasting sugar levels, but not with significant increases in hemoglobin A1c, a measure of long-term sugar control. With longer treatment, however, there was a significant rise in hemoglobin A1c, indicating impaired sugar control. In addition, there were also small changes in cholesterol levels among duloxetine-treated patients, but a small increase in HDL "good" cholesterol was the only statistically significant change. Weight declined with short-term duloxetine treatment, but increased slightly with long-term treatment.