<unk>  crosses the protective blood-brain barrier, whereas<unk> mine itself cannot. Thus,<unk>  is used to increase<unk> mine concentrations in the treatment of Parkinson's disease, Parkinsonism,<unk> mine-responsive dystonia and Parkinson-plus syndrome. The therapeutic efficacy is different for different kinds of symptoms. Bradykinesia and rigidity are the most responsive symptoms while tremors are less responsive to levodopa therapy. Speech, swallowing disorders, postural instability and freezing gait are the least responsive symptoms. Once<unk>  has entered the central nervous system, it is converted into<unk> mine by the enzyme aromatic -amino acid decarboxylase, also known as<unk>  decarboxylase. Pyridoxal phosphate (vitamin B6) is a required cofactor in this reaction, and may occasionally be administered along with<unk> , usually in the form of pyridoxine. In humans, conversion of<unk>  to<unk> mine does not only occur within the central nervous system. Cells in the peripheral nervous system perform the same task. Thus administering<unk>  alone will lead to increased<unk> mine signaling in the periphery as well. Excessive peripheral<unk> mine signaling is undesirable as it causes many of the adverse side effects seen with sole<unk>  administration. To bypass these effects, it is standard clinical practice to coadminister (with<unk>  a peripheral<unk>  decarboxylase inhibitor (DDCI) such as carbidopa (medicines containing carbidopa, either alone or in combination with<unk> , are branded as Lodosyn (Aton Pharma) Sinemet (Merck Sharp & Dohme Limited), Pharmacopa (Jazz Pharmaceuticals), Atamet (UCB), Syndopa and Stalevo (Orion Corporation) or with a benserazide (combination medicines are branded Madopar or Prolopa), to prevent the peripheral synthesis of<unk> mine from<unk> . Inbrija (previously known as CVT-301) is an inhaled powder formulation of levodopa indicated for the intermittent treatment of "off episodes" in patients with Parkinson's disease currently taking carbidopa/levodopa. It was approved by the United States Food and Drug Administration on December 21, 2018 and is marketed by Acorda Therapeutics. Coadministration of pyridoxine without a DDCI accelerates the peripheral decarboxylation of<unk>  to such an extent that it negates the effects of<unk>  administration, a phenomenon that historically caused great confusion. In addition,<unk> , co-administered with a peripheral DDCI, is efficacious for the short term treatment of restless leg syndrome. The two types of response seen with administration of<unk>  are: * The short-duration response is related to the half-life of the drug. * The longer-duration response depends on the accumulation of effects over at least two weeks, during which ΔFosB accumulates in nigrostriatal neurons. In the treatment of Parkinson's disease, this response is evident only in early therapy, as the inability of the brain to store<unk> mine is not yet a concern.
L-DOPA
D-DOPA
4-Methylaminorex
Phenserine
Fluorodopa
Nicotinamide
Glutamate 
Tuaminoheptane