Hi My 18 Year Old Son Has Been Diagnosed With

Hi my 18 year old son has been diagnosed with OCD and tics. This condition has been going on for almost 2 years. He is on meds prescribed by a doctor which is paroxetine 20mg. 2 tablets daily. Increased medication this week. He is consistently producing excessive saliva in his mouth holding on to it and then spitting it out. This is very embarrassing and he is doing year 12 at school. How do I help to reduce his saliva back to normal. Are their any off the shelf medication that can help. He is an appointment with psychiatrist this week. Do you have any suggestions which would be very helpful. Much appreciated.