I have a kinghell problem with glutamate (i.e. MSG, aspartame, etc). It literally shuts down my medications for four to eight hours. I can literally triple or quadruple my medication dose (requip or sinmet) and I might as well be eating candy. Nada!
The reaction comes on in ten to twenty minutes. Brainfog is a big part of it. Can't walk. Bladder switches into overdrive. Lovely combination.
Glutamate is the main stimulatory neurotransmitter. Dopamine is an inhibitory one. One of the ways that dextromethorphan works is to block glutamate. Another blocker is ibuprofen which prevents PD and leads some to suggest glutamate as one cause.
I ran across a forum post (NPF, I think) where a fellow had contacted Zandu with a similar concern over a corn allergy and was unable to get an answer from them.
Zandu is a division of one of India's biggest chemical companies and they are actively pushing "sugar-free" products without saying one way or the other.
I have been using Zandopa for about two weeks now with increasing unease. The last few nights I have awakened at 3:00 AM or so, unusual for me. And this morning my bladder let go upon standing up from the bed. Not the usual effect. Then I took the zandopa and was on in 30 min and back off at the 90 min mark with a couple more bladder surprises along the way. Took requip, sinemet, and another round of Zandopa about 5:00 AM - on at 6:00 and off at 8:00. Then I took 15 g of plain old mucuna at 2:00 and have been happy ever since.