Some 1,257 patients with diabetic neuropathy were randomly assigned to receive, in double-blind fashion, placebo or acetyl-L-carnitine (ALC) at a dose of 500 or 1,000 mg 3 times a day for 1 year. Compared with placebo, the lower dose of ALC resulted in a significant improvement in the O'Brien rank score, a measure of sural nerve fiber numbers and regenerating nerve fiber clusters. The higher dose of ALC was non-significantly more effective than placebo. Compared with placebo, significant improvements were seen in both treatment groups in vibration perception. Compared with placebo, the mean pain score improved significantly more with high-dose ALC; the improvement with low-dose ALC was similar to that in the placebo group. Patients with type 2 diabetes were more likely to experience a reduction in pain from high-dose ALC than were patients with type 1 diabetes.

Comment: These results suggest that ALC can relieve pain and improve nerve fiber regeneration and vibration perception in patients with diabetic neuropathy. By some measures, a dose of 1,500 mg/day was more effective than 3,000 mg/day, but by other measures the higher dose was more effective. Therefore, if ALC is used to treat diabetic neuropathy, the dosage should be individualized according to the patient's response. Other treatments that have been reported to be beneficial for diabetic neuropathy include evening primrose oil, vitamin B12 injections, and vitamin B6.

Sima AAF, et al. Acetyl-L-carnitine improves pain, nerve regeneration, and vibratory perception in patients with chronic diabetic neuropathy: an analysis of two randomized placebo-controlled trials. Diabetes Care 2005;28:89-94.