Parkinsonism. Clinical and neuropharmacologic aspects.

While the etiology of the most common form of parkinsonism (idiopathic) remains elusive, studies of the regional biochemistry and pharmacology of the brain have led to recognition of the importance of certain pathways, such as the nigrostriatal system. This information evolved from the discovery that the neurotransmitter dopamine is depleted in parkinsonism and that restoration of dopamine by administration of its precursor, levodopa, induces a dramatic therapeutic response in many patients. Such studies have initiated and sustained a major surge in neuropharmacologic advances, but the tangible benefits, in the form of therapeutic results, have undergone some critical reappraisal with the appearance of late adverse reactions to levodopa. One practical approach to this problem is deliberate delay in starting levodopa therapy and the use of lower doses. Use of artificial dopaminergic agonists and selective inhibitors of monoamine oxidase B has also been investigated.