The action of bupropion is not fully understood, but we know bupropion blocks both dopamine and norepinephrine from being reabsorbed, which means they hang around longer and work longer. Dopamine and norepinephrine are chemicals in the brain, called neurotransmitters, that send messages from one nerve cell to the next.
Bupropion seems to affect these these two important neurotransmitters in a way that is similar to nicotine, which can decrease your withdrawal symptoms when you are trying to quit. Bupropion also weakly blocks the nicotine receptor (the place on a nerve cell where a chemical lands to transmit its message), which makes smoking less pleasurable. This helps prevent relapse when former smokers are trying to make their new habit stick.
This information is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment, and should never be relied upon for specific medical advice. If you have any questions or concerns, please talk to your doctor.