The commonest form of Parkinsonism is idiopathic Parkinsonism or paralysis agitans (shaking palsy), the cause for which is unclear even today, though the pathognomonic feature is loss of pigmented, dopaminergic neurones of substantia nigra and appearance of intracellular inclusions (Lewy bodies).
Parkinsonism can also result from established causes such as toxicity (dopamine receptor-blocking drugs), adverse drug effects (antipsychotics such as haloperidol, antiemetics such
It is important to remember that anti –parkinsonian drugs are effective mainly in the treatment of idiopathic Parkinsonism, while in the other cases drugs usually do not produce much relief. These drugs include levodopa-carbidopa, levodopa-benserazide, dopamine receptor agonists such as bromocriptine and pergolide, MAOIs such as selegiline, muscarinic receptor antagonists such as trihexyphenidyl, benzotropine mesylate and diphenhydramine, and an anti-viral agent, amantidine.
Only those drugs which have not been discussed elsewhere will be discussed in this section.