The FDA has approved istradefylline (Nourianz — Kyowa Kirin), an oral adenosine A_2A receptor antagonist, for use as an adjunct to carbidopa/levodopa in adults with Parkinson's disease (PD) who experience "off" episodes. Istradefylline is the first adenosine A_2A receptor antagonist to be approved in the US; it has been available in Japan since 2013.

Apomorphine (Apokyn - Mylan/Bertek), an injected non-ergot dopamine agonist, was recently approved by the FDA for intermittent subcutaneous (SC) treatment of hypomobility ("off" episodes) in patients with advanced Parkinson's disease. It has been available in Europe for many years.

Levodopa combined with carbidopa (Sinemet) is the treatment of choice for Parkinson's disease (Medical Letter, 30:113, 1988). After prolonged treatment, however, the symptoms of the disease often become difficult to manage. The benefit from each dose becomes shorter (the 'wearing-off' effect), sudden fluctuations occur between mobility and immobility (the 'on-off' phenomenon), and abnormal involuntary movements (dyskinesias) may become frequent. The dopamine agonist bromocriptine (Parlodel) can ameliorate some of these effects. Two new drugs, pergolide (Permax - Lilly), another dopamine...

Deep brain stimulation (DBS) is increasingly used to treat advanced Parkinson's disease (PD), but few controlled clinical trials have been published. New evidence from a large controlled study has recently become available.

View the Comparison Table: Drugs for Parkinson's Disease

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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The dopamine agonist pramipexole (Mirapex - Boehringer Ingelheim) is the second drug approved by the FDA for treatment of moderate to severe restless legs syndrome (RLS). Ropinirole (Requip), another dopamine agonist, was approved for RLS in 2005. Both of these drugs were first approved for treatment of Parkinson's disease.

The motor symptoms of Parkinson's disease (PD) are caused primarily by degeneration of dopaminergic neurons in the substantia nigra. The nonmotor symptoms of the disease are thought to be caused by degeneration of other neurotransmitter systems. No disease-modifying drugs are available for treatment of PD.

Rasagiline (Azilect - Teva), a monoamine oxidase-type B (MAO-B) inhibitor, was recently approved by the FDA for once-daily oral treatment of Parkinson's disease (PD). It can be taken alone for treatment of early disease or with levodopa/carbidopa (Sinemet, and others) for advanced disease. Selegiline (Eldepryl, and others), the first MAO-B inhibitor marketed in the US, has been available since 1988; a new lower-dose disintegrating tablet (Zelapar) was recently approved.