Is Antioxidant Treatment with ALA Safe and Effective for Diabetic Polyneuropathy?

Lipoic acid enzyme cofactor moleculeGerman researchers investigated the safety and effectiveness of α-lipoic acid (ALA) over 4 years in patients with mild-to-moderate diabetic distal symmetric sensorimotor polyneuropathy (DSPN). Their study appeared in the September 2011 issue of Diabetes Care in an article called “Efficacy and safety of antioxidant treatment with {alpha}-lipoic acid over 4 years in diabetic polyneuropathy: the NATHAN 1 trial.”

The study—a multi-center randomized double-blind parallel-group trial—included 460 patients with diabetes who also had mild-to-moderate DSPN. Participants were randomly assigned to oral treatment with 600 mg of ALA once/day (n=233) or a placebo (n=227) for 4 years. The primary endpoint was a composite score (Neuropathy Impairment Score [NIS]-Lower Limbs [NIS-LL] as well as 7 neurophysiologic tests); NIS, NIS-LL, nerve conduction, and quantitative sensory tests (QSTs) were secondary outcome measures.

Researchers found that the change in primary endpoint from baseline to 4 years showed no meaningful difference between treatment groups (p=0.105). However, change from baseline was considerably better with ALA than the placebo for NIS (p=0.028), NIS-LL (p=0.05), and NIS-LL muscular weakness sub-score (p=0.045).

The results also showed that more participants had a clinically meaningful improvement, and fewer participants showed progression of NIS (p=0.013) and NIS-LL (p=0.025) with ALA than with the placebo. In addition, nerve conduction and QST results did not significantly deteriorate with the placebo.

It was also noted that global assessment of treatment tolerability and discontinuations because of lack of tolerability did not differ between the groups. However, the rates of serious adverse events were higher with ALA (38.1%) than with the placebo (28.0%).

Researchers concluded that 4-year treatment with ALA in mild-to-moderate DSPN did not have an effect on the primary composite endpoint, but it did result in a clinically meaningful improvement and prevention of progression of neuropathic impairments and was well tolerated. Because the primary composite endpoint did not considerably worsen in the participants treated with the placebo, secondary prevention of its progression by ALA according to the trial design was not possible.

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