What is Chemical Injury
Chemical injury -induced neuropathy is a potentially reversible form of neuropathy. Identification of toxicity is critical before significant axonal injury occurs. Many medications have limited or dubious evidence for toxicity. Certain individuals are more susceptible to neurotoxicity, especially those with existing neuropathy, specific genetic predispositions, or renal or hepatic insufficiency.
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Symptoms
- Tingling or numbness in the fingers, toes or legs
- Feeling cold, burning or pain in the hands, feet or legs
- Extreme sensitivity to touch, even a light touch
- Sharp pains or cramps
- Loss of balance and coordination
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Treatments
- Nonpharmacologic options include cool soaks, heat, massage, elevation or lowering of the limbs, shoe tightness, and/or exercise.
- Pharmacological options include tricyclic antidepressants, anticonvulsants, opiates, or topical capsaicin cream. Other options include intravenous gamma globulin, aldose reductase inhibitors, nerve growth factor, anti–tumor necrosis factor-α; these are mainly research ideas. Three that may be helpful presently include lipoic acid, evening primrose, and vitamin E.
- Alpha lipoic acid is well reviewed by Halat and Dennehy.[50] Thiolic acid is a free radical scavenger and chelator. It is approved for use in Germany for neuropathy. The best studies suggest parenteral use followed by oral use relieves symptoms and improves nerve blood flow. Oral preparations are available in United States. Two studies suggest increased nerve conduction (600/1200 mg for 2 y, oral) and reduced symptoms (1800 mg/d for 3 wk, oral). The mechanism of action includes chelation and, thus, a concern for mineral shortage exists. Monitoring iron levels is suggested, and persons with alcoholism need to take vitamin B.
- Evening primrose is also well summarized by Halat and Dennehy.[50] It includes omega 6 essential fatty acids: gamma linoleic acid (GLA) and linoleic acid. It is an essential component of myelin and the neuronal cell membrane. Dosages ranging from 360-480 mg/d for 6 months to 1 year improved nerve function measurements. It has mild side effects including inhibition of platelet aggregation. Concern also exists for those with seizure disorders.
- Vitamin E is discussed in the article Argyriou et al.[51] Vitamin E has been administered to patients on chemotherapy for prevention of neuropathy at doses of 600 mg/d during treatment and then for 3 months after treatment. A reduced peripheral neuropathy score has been noted. A neuroprotective effect has been described.
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