SAN DIEGO -- A prescription medical food that provides active forms of folate and vitamins B6 and B12 may provide some relief for patients with diabetic peripheral neuropathy, a placebo-controlled trial showed. But Metanx -- which contains L-methylfolate calcium, pyridoxal-5'-phosphate, and methylcobalamin -- did not improve the primary endpoint of the perception of vibration compared with placebo, according to Vivian Fonseca, MD, of Tulane University in New Orleans. There were, however, some important improvements on secondary endpoints of neuropathic symptoms and health-related quality of life, he reported at the American Association of Clinical Endocrinologists meeting here. In an interview, he said he thinks the results warrant further study, perhaps with a different primary endpoint. Fonseca said Metanx -- which is approved by the FDA and is indicated for the management of the nutritional requirements of patients with endothelial dysfunction, elevated homocysteine levels, or both who present with symptoms of diabetic peripheral neuropathy or lower extremity ulcerations -- might affect neuropathy because of the role vitamins play in nerve metabolism. Many diabetic patients have vitamin deficiencies, he said, noting that metformin lowers level of vitamin B12, which might affect nerve function. "It's not something we've paid a lot of attention to, but it might contribute in some way to the patient's neuropathy being worse," said Fonseca, who is president-elect for medicine and science of the American Diabetes Association. For now, clinicians might consider using Metanx for their patients with diabetic peripheral neuropathy to see whether it makes the patients feel better, he said. "It's available and there's nothing else" for diabetic neuropathy, Fonseca said, who acknowledged that because of the failure of Metanx to affect vibration perception there is no objective way to tell whether it is working. But, he said, "ultimately what matters is that the patients get better." The trial was a 24-week, double-blind, placebo-controlled study of 214 patients with type 2 diabetic peripheral neuropathy and a baseline vibration perception threshold of 25 to 45 volts. Their mean age was 62.6 (range 25 to 80), the mean duration of diabetes was 11.5 years, and symptoms of neuropathy were present for an average of 6.1 years. Either Metanx or placebo was taken orally twice a day. Medication compliance exceeded 95% in both groups. Patients were allowed to use other medications for diabetic peripheral neuropathy as long as the doses remained constant during the study. After 24 weeks, there was no difference between the groups in vibration perception threshold. "It did not change, but that's okay," Fonseca said. "There is no study for any drug in neuropathy that changes things like nerve conduction or vibration consistently in humans." There was, however, greater improvement with Metanx than with placebo on the Neuropathy Total Symptom Score-6 (at both 16 and 24 weeks), the Neuropathy Disability Score (at 16 weeks), and the mental component of the Short Form-36 Health Survey (at 24 weeks) (P<0.05 for all). Fonseca said that the doses of vitamins in Metanx will not cause toxicity, and that adverse events were infrequent in both arms of the study. No patients withdrew because of adverse events. The most common combined adverse events were infections and infestations (5.6%), injury, poisoning, and procedural complications (4.2%), and general disorders and administration site conditions (3.3%).