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Varenicline matters because it tackles nicotine addiction from two directions at once, relieving craving while also blocking the reward if the patient does smoke, rather than doing only one or the other. It is a partial agonistA drug that activates a receptor but produces a smaller effect than a full agonist, even at a high dose.Read more → (a drug that activates a receptor but only to a lower ceiling than the natural chemical) at the alpha-4-beta-2 nicotinic acetylcholine receptor, the same receptor subtype nicotine itself acts on. For example, imagine a patient trying to quit smoking who has a cigarette during a stressful moment: because varenicline is already occupying the receptor, the cigarette produces much less of the usual rewarding hit. In practice, this dual action, relieving withdrawal and blunting relapse, is what distinguishes varenicline from simple nicotine replacement.

As a partial agonistA drug that activates a receptor but produces a smaller effect than a full agonist, even at a high dose.Read more →, varenicline provides just enough alpha-4-beta-2 nicotinic receptor stimulation to ease craving and withdrawal symptoms, while also occupying the receptor so that nicotine from an actual cigarette cannot bind and produce its usual full reward. Treatment is started around one week before the planned quit date, allowing levels to build up before the patient tries to stop. Common side effects include nausea and vivid, sometimes disturbing dreams. For example, imagine a patient who begins varenicline a week before their quit date and reports vivid dreams in the first fortnight: this is an expected, usually self-limiting side effect rather than a reason to stop. In practice, this means counselling patients about likely nausea and vivid dreams in advance improves adherence to the full course.

• Compared with nicotine replacement and bupropion, how effective is varenicline for stopping smoking?
• Which adverse effect is reported most often by patients taking varenicline?
• Should varenicline be offered to a patient with stable schizophreniaA long-term mental illness involving episodes of psychosis such as hallucinations and delusions.Read more → who wants to stop smoking?

• Varenicline, partial nicotinic agonistA drug or chemical that activates a receptor to produce an effect.Read more → relieving craving and blocking cigarette reward, unlike bupropion, an antidepressant that works via dopamine and noradrenaline reuptake inhibition for smoking cessation.
• Nicotine replacement therapy (patches, gum): a full agonistA drug or chemical that activates a receptor to produce an effect.Read more → providing nicotine itself at lower, steadier levels, rather than varenicline's partial-agonist blocking action.
• Bupropion, also lowers seizure threshold and is contraindicated in epilepsy, whereas varenicline's main tolerability issues are nausea and vivid dreams rather than seizure risk.
• EAGLES trial findings, varenicline was not associated with significantly increased neuropsychiatric risk versus placeboAn inactive treatment given to a comparison group so any real effect of the active treatment can be judged against it.Read more → or patches, unlike earlier case-report-driven safety concerns that prompted the original boxed warning.

• It outperforms rather than underperforms the alternatives.
• Benefit is not restricted to light smokers.
• It is clearly superior to placeboAn inactive treatment given to a comparison group so any real effect of the active treatment can be judged against it.Read more → across trials.
• It works as monotherapy and is licensed as such.
• Joint swelling is not characteristic of this drug.

• 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.