L-dopa is an optically active form of dopa having L-configuration. Used to treat the stiffness, tremors, spasms, and poor muscle control of Parkinson's disease. It has a role as a plant growth retardant, an antiparkinson drug, a dopaminergic agent, a prodrug, a neurotoxin, a hapten, an allelochemical, an antidyskinesia agent, a mouse metabolite, a plant metabolite and a human metabolite. It is a L-tyrosine derivative, a dopa and a non-proteinogenic L-alpha-amino acid. Levodopa is the precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), used to treat Parkinson's symptoms.