New treatment options for pain caused by diabetic peripheral neuropathy were presented at the annual meeting of the American Academy of Neurology. While oral medications from 2 different drug classes appear effective, injection of botulinum toxin does not.
Lacosamide is an anticonvulsant that has shown some promise for control of neuropathic pain. Researchers from the United States and Europe examined long-term, open-label treatment with lacosamide for diabetic neuropathy in 2 studies.
Two-year interim results from the first trial indicated that more than 50% of 451 patients remained on treatment, with 42% receiving lacosamide for at least 18 months. Pain was reduced by a mean of 3.8 points (out of 11), an improvement that endured throughout the trial, and over 90% of patients reported their pain was “better” as a result of treatment. The 371 patients in the second trial, which lasted just over a year, also improved by a mean of 3.8 points, which was sustained over the course of the trial. In both studies, the most common adverse events were dizziness (affecting about 20% of patients), nausea (12%), and headache (10%).1
“In both trials, treatment was generally well tolerated,” according to Ronald Graf, MD, of Cedar Research, Tacoma, Washington, who characterized lacosamide as “a promising new treatment for painful diabetic neuropathy.”
Tapentadol is a centrally acting mu-opioid agonist and a norepinephrine reuptake inhibitor. In a new trial of an extended-release (ER) form of tapentadol, 591 patients received tapentadol ER during an open-label titration period. Treatment improved pain from a mean of 7.3 (severe) to 3.5 (mild) on an 11-point scale.
The 392 patients whose pain improved by at least 1 point were randomized to placebo or tapentadol ER at its effective dose for 12 weeks. Patients who received active treatment retained their improvement during the double-blind period, while those who received placebo worsened. Adverse events caused 15% of patients who received the drug to withdraw during the study; the most frequent effects were GI disorders and anxiety.2
Botulinum toxin type A (BoNT-A) has been tried in a number of painful conditions, including headache and low back pain, with mixed results. A small trial presented here suggests it has “minimal effects” in diabetic peripheral neuropathy, according to lead study author Michael Jacoby, MD, of Mercy Ruan Neurology Clinic in Des Moines, Iowa. Twenty-one patients were randomized to receive 1 of 2 doses of BoNT-A or placebo, injected at 4 sites into the foot. Patients who received BoNT-A reported significant improvement on one section of 1 pain scale, but there was no clear demonstration of benefit on 2 other scales. Nonetheless, because some of the results were suggestive of an effect, and because outcomes in a recent similar study from Taiwan were more promising, Jacoby said further studies in larger groups of patients are warranted.3
1. Graf R, Frye W, Simpson J, et al. Long-term treatment of diabetic neuropathy with lacosamide: results from two long-term open-label trials [P05.019]. Poster presentation, April 29, 2009.
2. Etropolski M, Shapiro D, Okamoto A, et al. Efficacy and safety of tapentadol ER for diabetic peripheral neuropathic pain: results of a randomized-withdrawal, double-blind, placebo-controlled phase III study [P05.047]. Poster presentation, April 29, 2009.
3. Jacoby MR, Hughes B, Finnerty EP. Botulinum toxin (type A) for the treatment of diabetic peripheral neuropathic pain [P05.041]. Poster presentation, April 29, 2009.