Wellbutrin XL (bupropion) is an oral medication used primarily to treat major depressive disorder and seasonal affective disorder (SAD, a form of depression that occurs in the fall and winter). It may also be sometimes used to treat attention deficit hyperactivity disorder (ADHD), and depression in patients with bipolar disorder. It is part of a class of medications called antidepressants, and is suspected to work mostly by inhibiting the reuptake of norepinephrine and dopamine in the brain.
It is believed that a possible cause of depression is a low amount of the neurotransmitters norepinephrine and dopamine, among others. In the brain, the space between where two neurons meet to communicate is called a synapse, and the synapse is where norepinephrine, dopamine, and other neurotransmitters are used to communicate between neurons. In depression, people may not have enough norepinephrine and dopamine in their brain. Normally after a chemical message is sent between neurons, the neurotransmitters are reabsorbed by the sending neuron (presynaptic neuron).
A selective norepinephrine-dopamine reuptake inhibitor will bind to the presynaptic neuron and prevent it from absorbing the norepinephrine and dopamine, and leave the neurotransmitters active in the synapse, improving mood and anxiety symptoms.