I Have A Brother Who Has Parkinson Disease. He Is

I have a brother who has Parkinson disease. He is on levodopa carbidopa 25 mg. 3 times a day, plus mirtazapine 15 mg.at bedtime. About an hour after he takes the mirtazapine he suffers for about an hour and a half with an awful feeling that he cannot describe. He is also extremely "shaky' (HANDS AND SHOULDERS especially. Should he be on a drug for this shakiness such as Azilect?. He is a very passive patient and continues to suffer and does not return to his doctor to discuss his continuing issues with symptons.
Thank you for considering this question.