What Causes Problems In Digestive System After Taking Syndopa, Pacitine And Ropark?

My father is 57 and he is suffering from a disease similar to Parkinsons since almost 20 yrs. Earlier he use to take Levodopa. Now since 1.5 yrs he is taking Parkitdin, Epilong 0.5 and Duracetam Syrup. He is also taking Syndopa, Pacitine and Ropark alongwith above mentioned medicines with a gap of 2 hrs approx. He takes four doses of both the set of medicines as prescribed by doctor. I want to know whether is it necessary to take both set of medicines. Also his digestive system is not good and he is getting thin day by day. Is it a side effect of any medicines.