I began posting on this subject back in 2005 on the old braintalk forum. As described in my posts earlier on this long thread, I have been faithfully taking 3.5-5mg of DM in pediatric cough syrup each night at bedtime since sometime in 2005. Therefore, I think that makes me the longest-term user of this approach to attempt neuro protection for PD.

The result has been that I feel that I have experienced quite significant slowing of progression of my Parkinson's disease symptoms. However there has been a slow, steady increase in the doses of sinemet required to allow me to maintain good control of my symptoms, bradykinesia, balance difficulties, shuffling gait, and some postural instability. I have increased from 100mg of IR carbi/levo 3X daily in 2001 when diagnosed, to one each of 100mg IR and 200mg of CR 3X daily, at 5 hour intervals. I occasionally forget to take the second or third dose. If more than a couple of hours late, my symptoms faithfully remind me of the error. Once "off", however, it is difficult to get back truly "on" after taking the skipped dose.
I have never had significant tremor. When I am "on", which is about 90% of my waking hours, my gait is essentially normal, and I am not seriously limited in endurance. Until the last few weeks I have also taken 900-1200 mg of CoQ12 daily. I plan to resume the CoQ10 because I sense that my symptoms have begun to be more apparent.

I would, like staurus/David, also like to hear from as many of you as are willing to share your experience with dextromethorphan in attempting to slow progression of Parkinson's disease.

Robert