L-Dopa for ADHD

L-dopa (levodopa, L-3,4-dihydroxyphenylalanine) is an amino acid that is formed from tyrosine by tyrosine hydroxylase and is a precursor of dopamine, noradrenaline and adrenaline, among others.
Unlike dopamine, noradrenaline and adrenaline, levodopa can cross the blood-brain barriers. Once L-dopa enters the brain, it is converted to dopamine and is therefore a dopamine prodrug.

L-dopa is often used to treat Parkinson’s disease.
It has not yet proven to be effective in the treatment of ADHD. Like dopamine agonists (amantadine), it does not significantly improve hypermotor skills, impulsivity or attention.¹

One study found that the increased leg movements of ADHD sufferers during sleep were unaffected by L-dopa,² although restless legs are often treated with L-dopa.³

A survey revealed indications that in the rare cases of postsynaptic dopamine receptor hypersensitivity (DARSS), therapy with very low doses of levodopa (VLDT) of 0.5-1 mg/kg/day could also be helpful in relation to ADHD symptoms.⁴

Amphetamine drugs appear to increase L-dopa levels by activating tyrosine hydroxylase in the dorsal striatum and nucleus accumbens. However, this does not appear to occur via a change in the phosphorylation of tyrosine hydroxylase.⁵