Talk to Gastroenterologist on Gastrointestinal

Aoa. My father has Parkinson's disease and is on medications. Since last month he is having very hard stools and that too after 2 3 days gap. It's very time taking and painful for him to pass stool. Neurophysician advised skillax. Is there any better alternative. We gave him skillax 3 drops but it didn't work. Then gave him 7 drops next day which caused him motions. What should be actual dose. We are giving him lots of fibre in form of pears and apples. And he drinks plenty of water. But nothing helps.