The FDA has approved Crexont (Amneal), an extended-release capsule formulation of carbidopa/levodopa, for treatment of Parkinson's disease (PD), postencephalitic parkinsonism, and parkinsonism associated with carbon monoxide or manganese intoxication. Crexont contains a combination of immediate-release carbidopa/levodopa granules and extended-release levodopa pellets. An extended-release carbidopa/levodopa oral capsule (Rytary) has been available from the same manufacturer for years; the patent for Rytary expires in 2025.

Vyalev (Abbvie), a solution for continuous subcutaneous infusion containing the prodrugs foscarbidopa and foslevodopa, has been approved by the FDA for treatment of motor fluctuations in adults with advanced Parkinson's disease (PD). Vyalev is the first subcutaneously administered product to become available in the US for treatment of PD symptoms. Duopa, a carbidopa/levodopa enteral suspension infused via a nasojejunal tube or percutaneous gastrostomy, was approved in for the same indication 2015.

A selective serotonin reuptake inhibitor (SSRI) is generally used for initial treatment of major depressive disorder (MDD). A serotonin-norepinephrine reuptake inhibitor (SNRI), bupropion (Wellbutrin SR, and others), and mirtazapine (Remeron, and others) are reasonable alternatives. Improvement in symptoms can occur within the first two weeks of treatment with these drugs, but a substantial benefit may not be achieved for 4-8 weeks.

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.