Actually just saw news about a presentation at this year's international parkinson's congress demonstrating that a special combination of probiotiics effectively relieves constipation in pd. Unfortunately, the pill is not yet available commercially. The authors stated that they hoped to be able to manufacture a less expensive version that would be commercially available. Wouldn't that be great?!!

Definitely high protein food affects the absorption of Sinemet. Also, sorry to get down to. basics but constipation plays a major part in the affects of medication.

I would vomit whenever I took C/L at first. I now take always take it with a small dose of an antiemetic (not available in the US; only from certain Canadian pharmacies) called domperidone. Nearly all other antiemetics interfere with the action of C/L and cannot be used. The US FDA has 'cracked down' on pharmacies from Canada sending this medication across the border, although it is actually perfectly legal for your physician to write a prescription for it. (Long story about why it's not available in the US). In most of the rest of the world, it is an over the counter medication. However, recent studies suggest that higher doses may be associated with cardiac changes. Low doses do not show changes. Anyway, it's something to explore. If you or a friend is traveling abroad, it is pretty easy to get it in other countries. I often pick up a bunch when traveling.
I say that domperidone is an 'antiemetic' meaning that it reduces nausea. If that is the symptom that your wife is experiencing, it may help. Domperidone helps gastric motility/movement which can slow down in Parkinson's Disease, making digestion of C/L particularly difficult.
Hope this helps.

It's generally recommended to take Levodopa with food to lessen the side effects.It has worked for me when I started treatments in 2011

Have docs ruled out a diagnosis of Llewy Body dementia? I ask because it is characterized by Parkinson's type tremors and simultanous dementia.
In any case, my heart goes out to you. I look at sleep as a way of naturally withdrawing when the world is exhausting to process . I have pd as well as my dad but he did not develop dementia until living with pd for nearly 30 years. I might ask you other questions which could help clarify the specific diagnosis but part of me thinks that, when a loved one has lost themselves to dementia, the specific diagnosis is of greater importance to the docs than you. Your loss is the same.
Wishing you peace and strength.
Karenr