You should ask the GP for a referal to the SALT team (speech and language therapy) they deal with issues like this although their name doesn't suggest it.
There have been residents in care with my wife who used to spit on the floor audit turned my stomach every time they did it.
My wife is under the SALT team as she's losing her swallow reflex and does choke a bit on her own saliva sometimes, as we produce a small amount of saliva all the time we have a built in swallow reflex embedded into us so it may not be an"excess" it's that the body can no longer manage the situation and forgets to do something we all do hundreds of times a day without noticing.
K