L 3,4 Dihydroxyphenylalanine
The naturally occurring form of Dihydroxyphenylalanine and the immediate precursor of Dopamine. Unlike Dopamine itself, it can be taken orally and crosses the Blood-Brain Barrier. It is rapidly taken up by Dopaminergic Neurons and converted to Dopamine. It is used for the treatment of Parkinsonian Disorders and is usually given with agents that inhibit its conversion to Dopamine outside of the Central Nervous System.