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Bupropion's mechanism matters because it explains why it avoids the sexual side effects that limit many other antidepressants, while carrying a seizure risk they do not. It is a noradrenaline-dopamine reuptake inhibitor (NDRI), a drug that blocks the reuptake of noradrenaline and dopamine back into the presynaptic neuron so more remains active in the synapseThe tiny gap between two nerve cells where a chemical signal passes from one to the other.Read more →. For example, imagine a patient on an SSRISelective serotonin reuptake inhibitor, a common type of antidepressant.Read more → (selective serotonin reuptake inhibitor) who stops treatment because of low libido: switching to bupropion, which does not raise serotonin, often resolves the problem. Because it raises dopamine rather than serotonin, bupropion also has a use unrelated to mood, helping people stop smoking.

Bupropion is licensed for both depression and smoking cessation, and its dopamine-boosting action likely underlies its usefulness for low energy and poor concentration. Unlike SSRIs, it causes no sexual dysfunction and little weight gain, which makes it attractive for people who cannot tolerate those effects. Its major risk is a lowered seizure threshold, so it is contraindicated in epilepsy and in eating disorders such as bulimia nervosa (a disorder of binge eating and compensatory purging), where electrolyte disturbance also raises seizure risk. Take a smoker with depression and no seizure history: bupropion can treat both problems at once. In practice, clinicians always screen for epilepsy and eating disorders before prescribing it.

• A man is switching from phenelzine to bupropion. What is the minimum interval that should be left between stopping the first drug and starting the second?
• A woman on bupropion is started on risperidone, and her antipsychotic levels rise unexpectedly. Inhibition of which enzyme by bupropion best explains this?
• A smoker is prescribed bupropion to help him stop. How should the timing of his quit date relate to starting the medication?
• A researcher explains why bupropion has been trialled in attention-deficit hyperactivity disorder. Which pharmacological property provides that rationale?

• SSRISelective serotonin reuptake inhibitor, a common type of antidepressant.Read more → (selective serotonin reuptake inhibitor): raises serotonin and commonly causes sexual dysfunction, unlike bupropion which targets noradrenaline and dopamine instead.
• Varenicline, a nicotinic receptor partial agonistA drug that activates a receptor but produces a smaller effect than a full agonist, even at a high dose.Read more → licensed for smoking cessation, whereas bupropion works indirectly through dopamine and noradrenaline reuptake blockade.
• Tricyclic antidepressants, also lower seizure threshold, but bupropion's risk is disproportionately high for its antidepressant dose, unlike most tricyclics.
• Mirtazapine, a sedating antidepressant that increases appetite and weight, unlike bupropion which is typically weight-neutral or associated with modest weight loss.

• That enzyme is not the one this drug notably inhibits.
• That enzyme is induced by smoking rather than inhibited by this drug.
• A single day leaves the enzyme still substantially inhibited.
• A few days is insufficient for enzyme regeneration.
• A week still leaves meaningful enzyme inhibitionA drug reducing the activity of a liver enzyme, which slows the breakdown and raises the level of other drugs sharing that enzyme.Read more → present.

• Identify the drug, receptor, enzyme or pharmacokinetic change named in the stem.
• Translate it into the immediate mechanism before looking at the options.
• Use timing and the adverse-effect pattern to separate the nearest alternatives.
• Check whether the question asks for mechanism, clinical consequence, monitoring or management.