L Tyrosine vs. Dextroamphetamine In a sleep deprivation study, L Tyrosine actually outperformed one of Adderall's active stimulants (dextroamphetamine) in key cognitive tests, like mathematical processing and logical reasoning, even after 30 hours with Enzymatic Phosphorylation of Oxidized Tyrosine Residues Figure 2. [The tyrosine degradation pathway. Alkaptonuria]. GeneReviews NCBI Bookshelf The role of tyrosine hydroxylase dopamine pathway in Parkinson's disease pathogenesis Research Communities by Springer Nature