Once a diagnosis of idiopathic
parkinsonism has been made, the choice and timing of
therapy depend almost entirely on the patient's need for symptomatic relief, as no presently available
therapy has any effect on the pathogenesis of the disease. Five categories of drugs are available for the treatment of idiopathic
parkinsonism.
Anticholinergic agents are effective against
tremor but have prominent adverse effects.
Amantadine has similar effects but is more active against rigidity and
bradykinesia.
Selegiline is a
monoamine oxidase-B inhibitor; once thought to affect the pathogenesis of idiopathic
parkinsonism, it is now known to offer only symptomatic relief. The
dopamine agonists (
bromocriptine,
pergolide, and
lisuride) stimulate D2 receptors; they have antiparkinsonian effects and tolerance profiles broadly similar to those of
levodopa but are slightly less efficacious.
Pleural effusions and
pulmonary fibrosis are unusual but important complications of these drugs; chest x-ray examinations are therefore recommended for all patients starting such treatment.
Levodopa (combined with an extracerebral
decarboxylase inhibitor to prevent
nausea, the main adverse effect) has become the standard antiparkinsonism treatment. Patients using this preparation can suffer considerable variations in mobility and
dyskinesia, which may be related to rapid, large-scale oscillations in plasma
levodopa concentrations. Controlled-release (CR) preparations have been developed in an attempt to minimize these fluctuations and reduce long-term side effects. There is no universally agreed treatment for idiopathic
parkinsonism. However, experience shows that a good balance of antiparkinsonian activity and adverse effects can be obtained by initiating treatment with a combination of
levodopa and a
decarboxylase inhibitor. A
dopamine agonist can be added if the disease progresses and increased therapeutic activity is required.