Invisible, I am still taking 3.5-4.0 mg of dextromethorphan, in addition to other typical PD meds (carbidopa/l-dopa, amantadine), and progressing pretty slowly. My use of DM (or DX) amounts to an over-the-counter substitute for low-dose naltrexone (LDN), if you have heard of that. There are several neurodegenerative diseases, PD and MS in particular, that often respond to these drugs by slowing or arresting progression of symptoms. As lurkingforacure suggested, you can get the complete story on DM and LDN by searching my old posts, or just dextromethorphan on this forum.

There is a whole lowdosenaltrexone web site if you are interested in getting more detail on that. Naltrexone requires a prescription, however, and its use for these purposes is "off label".

Incidentally, I discovered that "Pedia Care - Simply Cough", the pediatric cough syrup preparation of DM I have been using has been recalled. When I tried to purchase some at CVS a couple of days ago, I took it to check out but the bar scanner denied registering it in the system. When the clerk checked with the pharmacist, she was told that it has been recalled. She then went and removed the remaining bottles from the shelf and refused to sell it to me. The pharmacist then suggested that I use a CVS brand in which the DM concentration is two times higher than the Pedia Care preparation. This complicates the dosage that I take each night at bedtime since 1/4 tsp of the CVS product is harder to measure than 1/2 tsp of Pedia Care.
If I were paranoid, I could see a conspiracy of Big Pharma and the FDA to interrupt the attempts of us "white rats" at neuroprotection.

Robert