L-DOPA (L-3,4-dihydroxyphenylalanine) is a chemical that is made and used as part of the normal biology of humans, some animals and plants. Some animals and humans make it via biosynthesis from the amino acid L-tyrosine. L-DOPA is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline) collectively known as catecholamines. L-DOPA can be manufactured and in its pure form is sold as a psychoactive drug with the INN levodopa; trade names include Sinemet, Parcopa, Atamet, Stalevo, Madopar, and Prolopa. As a drug it is used in the clinical treatment of Parkinson's disease and dopamine-responsive dystonia. L-DOPA has a counterpart with opposite chirality, D-DOPA. As is true with many molecules, the human body makes only one of these isomers (the L-DOPA form).