Parkinson's is not a stable disease. As the disease progresses, the symptoms of parkinsonism become increasingly serious, new symptoms develop and people with Parkinson's disease get more and more affected by them. At the beginning of the disease, the symptoms can be suppressed with medication, but later on, it is becoming less successful. In the advanced stage of the disease, symptoms resulting from excessive dopaminergic stimulation (e.g., agitation, or hallucinations) and too little dopaminergic stimulation (e.g., inertia, tremors) alternate.