Which smoking cessation medication may cause vivid dreams as a side effect?

Varenicline is known to potentially cause vivid dreams as a side effect due to its action as a partial agonist at the nicotinic acetylcholine receptors in the brain. It works by stimulating these receptors, which can enhance dopaminergic activity and affect sleep architecture, leading to changes in the dream state. This unique mechanism can contribute to a more vivid or unusual dream experience for some users.

The other medications listed do not typically share this side effect. For instance, bupropion, while it can also affect mood and brain chemistry, is more commonly associated with a risk of insomnia rather than vivid dreams specifically. Nicotine gum and nicotine patches are primarily forms of nicotine replacement therapy and do not generally influence dream patterns in the same way that varenicline does. Thus, the side effect of vivid dreams is specifically linked to the use of varenicline in smoking cessation treatment.