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.