Attention deficit hyperactivity disorder management
There are two major medications derived from methylphenidate's isomers: a racemic mixture of half d-threo-methylphenidate and half l-threo-methylphenidate called methylphenidate (Ritalin, Concerta), and an enantiopure formulation containing just d-threo-methylphenidate called dexmethylphenidate (Focalin).
Norepinephrine transporter
Certain antidepressant medications act to raise noradrenaline, such as serotonin-norepinephrine reuptake inhibitors (SNRIs), norepinephrine-dopamine reuptake inhibitors (NDRIs), norepinephrine reuptake inhibitors (NRIs or NERIs) and the tricyclic antidepressants (TCAs). The mechanism by which these medications work is that the reuptake inhibitors prevent the reuptake of serotonin and norepinephrine by the presynaptic neuron, paralyzing the normal function of the NET. At the same time, higher levels of 5-HT are maintained in the synapse increasing the concentrations of the latter neurotransmitters. Since the noradrenaline transporter is responsible for most of the dopamine clearance in the prefrontal cortex, SNRIs block reuptake of dopamine too, accumulating the dopamine in the synapse. However, DAT, the primary way dopamine is transported out of the cell, can work to decrease dopamine concentration in the synapse when the NET is blocked. For many years, the number one choice in treating mood disorders like depression was through administration of TCAs, such as desipramine (Norpramin), nortriptyline (Arentyl, Pamelor), protriptyline (Vivactil) and amoxapine (Asendin). SSRIs, which mainly regulate serotonin, subsequently replaced tricyclics as the primary treatment option for depression because of their better tolerability and lower incidence of adverse effects.