I apologise in advance. I saw this was a previous question, but it was closed and I couldn't see any response from people. I'm desperately seeking advice for the drooling, it's gotten so bad I'm scared my brother will choke to death on his own saliva...
When you say stage 4- which is where my mother is- Im assuming you are unable to even consider the botox at this point,
The saliva thing/swallowing/drooling/phleghm is all part of the Parkinsons disease. as is the side effect from the sinemet. Kind of a double edge sword- just went through aspiration and pneumonia from this whole swallowing issue, Using thickeners for water and day by day here. Hope you can get something that works.
In the meantime, prop those pillows up when he is lying down and if the drool is not thin- more mucousy then see about using a guafenessian cough syrup (no dm) to thin it out so he can get it out. Also pay extra attention during this time to dental care.
chewing gum or sucking a lollipop can help to stimulate swallowing
transdermal scopolamine skin patches
botox injections