Which of the following agents is used for smoking cessation?

Nicotine is a key agent used for smoking cessation because it plays a significant role in helping individuals reduce withdrawal symptoms and cravings associated with quitting smoking. Nicotine replacement therapies, such as patches, gums, lozenges, and inhalers, deliver controlled amounts of nicotine to ease the transition away from tobacco use. This aids in managing the addictive aspects of smoking and supports the individual in breaking their dependence on tobacco.

Esomeprazole, a proton pump inhibitor, is primarily used to treat gastroesophageal reflux disease (GERD) and conditions caused by excessive stomach acid. Montelukast is a medication for asthma and allergic rhinitis, working as a leukotriene receptor antagonist to relieve respiratory issues. Lastly, diphenoxylate with atropine is an antidiarrheal medication used to manage diarrhea, with no role in smoking cessation. Thus, nicotine is the only agent listed that directly supports the effort to stop smoking.