LDN, save your money.
I came across ldn 10 years ago when they said my wife had MS. Turned out to be Parkinson's. My wife started taking ldn 10 years ago. Hard to get and expensive. She took it consistantly for the following 7 years. She gave up on it because she continued to progress where, now, she is severly disabled and at the place where many people with PD are after 12 years.
I did a lot of reading on ldn and was a believer but I no longer am. You can follow my ashleyk thread on Neurotalk Parkinson's, ldn dxm. If you want an equivalent opioid type drug for neuroprotection, look into dextromethorphan dxm (CVS cough syrup, 1/2 tsp day). It is easy to get, much cheaper and you know what you bought,
John

http://www.ncbi.nlm.nih.gov/pubmed/1...?dopt=Abstract
http://jpet.aspetjournals.org/content/305/1/212.full
http://www.fasebj.org/content/19/6/550.full