Parkinson's disease : Parkinson's disease (PD also known as idiopathic or primary Parkinsonism, hypokinetic rigid syndrome/HRS, or paralysis agitans) is a degenerative disorder of the central nervous system. The motor symptoms of Parkinson's disease result from the death of dopamine-generating cells in the substantia nigra, a region of the midbrain; the cause of this cell death is unknown. Tremor, rigidity, bradykinesia, and postural instability are the cardinal features of Parkinsonism and may be present in any combination. There may also be a mild decline in intellectual function. The tremor of about four to six cycles per second is most conspicuous at rest, is enhanced by emotional stress, and is often less severe during voluntary activity. Although it may ultimately be present in all limbs, the tremor is commonly confined to one limb or to the limbs on one side for months or years before it becomes more generalized.
Commonly used drugs in Parkinson disease include Levodopa-Carbidopa combination, Anticholinergics (orphenadrine , procyclidine ,trihexyphenidyl ), Dopamine Agonists( Bromocriptine, Carbergoline, Ropinirole, Pramipexole and Lisuride.), COMT inhibitors (entacapone ,Tolcapone) and MAO-B inhibitors ( rasagiline,selegiline)