Critical appraisal of the use of alpha lipoic acid (thioctic acid) in the treatment of symptomatic diabetic polyneuropathy

BACKGROUND The most common of the neuropathies associated with diabetes mellitus, diabetic sensorimotor polyneuropathy (DSPN) is a syndrome of diffuse, length-dependent, symmetric nerve dysfunction. The condition is linked with substantial morbidity, frequent healthcare utilization, and compromised quality of life due to related discomfort. Correspondingly, antidepressants, anticonvulsants, and opioids are regularly prescribed with the goal of pain control. However, the agents rarely provide complete pain relief and fail to address progression of the disorder. Whereas strict blood glucose control can slow the onset and worsening of DSPN, near-normoglycemia is not easily attainable. Evidence implicating oxidative processes in the pathogenesis of DSPN offers one potentially important therapeutic avenue. Due to its properties as a potent antioxidant, alpha lipoic acid (ALA) could mitigate the development of DSPN and attenuate resultant symptoms and signs. Approved for treatment of DSPN in Germany, the agent is not more widely used due to uncertainty about its efficacy and reported adverse effects. Here we review the effectiveness and tolerability of ALA in the treatment of symptomatic DSPN. METHODS The MEDLINE, EMBASE, and Cochrane Library databases were searched for English-language literature on the topic. Randomized, blinded studies comparing parenteral and oral ALA with placebo in the treatment of peripheral neuropathy in diabetic adults were selected. Analysis included studies with a level of evidence of at least 2b. RESULTS The current appraisal summarizes data from 1160 participants in the ALADIN, SYDNEY, ORPIL, SYDNEY 2, and ALADIN III trials. In four of the studies, ALA provided significant improvement in manifestations of DSPN. CONCLUSION Treatment with ALA 600 mg iv daily for 3 weeks represents a well-tolerated and effective therapy for DSPN. An oral dose of 600 mg daily administered for up to 5 weeks could offer benefits in symptoms and signs of DSPN without significant side effects.