You have already received good advice and helpful links. Everyone is different in their response to treatments for CRPS. I have received relief from the cold type of CRPS with ketamine infusions. I was on LDN but only briefly because of side effects. I just happen to be sensitive to many drugs. The dose I received was prepared by a compounding pharmacy and was expensive even with decent prescription insurance. It must be prescribed and I would not use an online service unless your doctor approves it. There are some disreputable sites out there.

You also need to make sure that you are dealing with doctors who are experienced with CRPS. Ask your doctor for a list of the best hospitals, universities, and experts in this field. A reputable doctor will not take offense and should have that information available. I was fortunate to have a doctor who referred me for the help I needed and all the doctors that I have to deal with are willing to share information and advice.

Sending good thoughts and prayers for successful treatment.