There has been some discussion about ammino acids in the past in re: to prorphial neuropathy.
It was mentioned amongst others in the interview with Dr. Gorter:
Xeloda does have minor side effects such as loose stool but the significant side effect is proriphial neuropathy which can practically be prevented by the increased intake of alpha-lipoic acid. You can counter this side effect by taking 600mg of alpha-lipoic acid which essentially, is a fatty acid. However, you cannot take alpha-lipoic acid during the period of the intake of Xeloda since the effect would be inhibited, but in many instances neuropathy can be prevented by taking alpha-lipoic acid during the two-week break.
THIS INFORMATION IS NOT INTENDED NOR IMPLIED TO BE A SUBSTITUTE FOR PROFESSIONAL MEDICAL ADVICE. YOU SHOULD ALWAYS SEEK THE ADVICE OF YOUR PHYSICIAN OR OTHER QUALIFIED HEALTH CARE PROVIDER