The accidental ingestion of Karwinskia humboldtiana causes a flaccid, symmetrical, progressive and ascending paralysis, similar to Guillain-Barre syndrome. It evolves over the course of 3 to 12 months until full recovery, but severe cases end in death due to respiratory failure. There is no specific treatment. The histopathological lesions described in peripheral nerve of patients and in experimental animals, corresponds to segmental demyelination accompanied by Wallerian degeneration. One of the toxins extracted from the seed, T-514, causes an increase of free radicals in vitro. Free radicals have been associated to demyelination that occurs in other types of neuropathy such as diabetic neuropathy. Since the ultrastructural damage that occurs in animal models of diabetes is similar to that observed in experimental poisoning with the fruit of K. humboldtiana, we decided to administer a powerful antioxidant, a-lipoic acid, in a model of chronic poisoning due of K. humboldtiana. However, no improvement was observed on the clinical manifestations evaluated in animals or in the histopathological lesions in the peripheral nerve. These results suggest that free radicals are not the primary mechanism of injury on the peripheral nerve caused by K. humboldtiana.