Levodopa: This would likely benefit this patient. It is the medication of choice in the treatment of Parkinson's disease because it increases dopamine levels in the brain.

This patient is likely suffering from Parkinson's Disease, characterized by a deficiency of dopamine in the brain's striatal region. Metoclopramide is a D2 dopamine receptor antagonist in the chemoreceptor trigger zone and therefore should be avoided as it could potentially worsen the symptoms of Parkinson's Disease.

Donepezil: This medication would not likely have a negative impact. It is an acetylcholinesterase inhibitor used in Alzheimer's disease and does not affect dopamine levels.

L-dopa: This would likely benefit this patient. It is similar to Levodopa and is also used in the treatment of Parkinson's disease.