Although it appears most ADHD drugs work by increasing dopamine they do not do so in the same way Parkinsons drugs (LDOPA)
do.
Part of the problem is that anti-parkinson drugs are designed to boost dopamine levels in a different region of the brain from the region where such deficits result in ADHD.
The thing is, anti-parkinson drugs work by boosting levels of the precursors to dopamine, the chemicals that the body uses to put dopamine together, essentially. Using these drugs can increase the amount of dopamine available within the cell, which is referred to as vesicular dopamine, because it is stored in little baggies called vesicles within the brain cells. Vesicular dopamine is then available for the cell to send out into the region between brain cells, called the synapse, where it acts as a chemical signal to a nearby cell. When dopamine exists the presynaptic cell into the synapse, it can be referred to as synaptic dopamine. Synaptic dopamine levels can be influenced by vesicular dopamine levels in some situations, and apparently many researchers believe that low synaptic dopamine levels in parkinson's patients are a result of low vesicular dopamine levels, and thus it makes sense to give them L-dopa as a means of boosting production of dopamine within certain brain cells.
By contrast, while ADHD does appear to result from, or at least involve low synaptic dopamine levels in certain striatal, prefrontal, and frontal regions of the brain, the majority of research appears to show that this is not influenced by vesicular dopamine levels. The presynaptic cells have plenty of dopamine, in other words, and the reason for the lack of dopamine in the synapse is due to something else, in this case the excess of dopamine transport proteins on the cell membrane, which remove the dopamine from the synapse. Too many transport proteins (I've seen estimates around 70% higher in ADHD persons) means that too much dopamine is removed from the synapse too quickly, and thus boosting the amount within the cell is not going to help much.
Most ADHD medications affect dopamine transporters, along with transport proteins for a related chemical called norepinephrine. Norepinephrine has also been implicated as being involved in ADHD, and additionally norepinephrine transport proteins may also be capable of removing dopamine from the synapse.
This is why one would use Adderall on an ADHD patient (causes transport proteins to work in reverse), but not on a Parkinson's patient, and why L-Dopa would work on a Parkinson's patient and not on an ADHD patient.
May not want to ditch the Adderall in exchange for Prolactrone.