How Quit-Smoking Medicines Work: Nicotine Replacement, Bupropion and Varenicline

Nicotine replacement therapy

• Nicotine replacement therapy (NRT) replaces some of the nicotine you used to get from cigarettes, so quitting is less uncomfortable. The U.S. Food and Drug Administration has approved five kinds, all with nicotine as the active ingredient. Patches, gum and lozenges are the most common quit-smoking medicines and can be bought without a prescription.
• NRT supplies nicotine without the hundreds of harmful chemicals in cigarette smoke.
• Used as directed, it gives most people enough nicotine to avoid overwhelming cravings and withdrawal symptoms — though even with medicine you will probably still feel some discomfort and urges to smoke, and there are many ways to get help with them.
• Wearing the long-acting patch together with a short-acting NRT such as the lozenge or gum can reduce withdrawal even more.
• You can taper the nicotine from NRT over several weeks. Your brain gets used to working with less nicotine, and you learn how to get through the day without smoking.

Nicotine changes the brain. This CDC film shows what happens when you smoke a cigarette, and how nicotine replacement therapy can help you quit for good. CDC, Tips From Former Smokers.

Quit-smoking pills

The FDA has approved two quit-smoking medicines that are pills: bupropion and varenicline.

• Bupropion has many effects on the brain, including helping people quit: it reduces craving and other symptoms of nicotine withdrawal.
• Varenicline does two things. It mimics some of nicotine's effects on the brain, reducing the urge to smoke and some withdrawal symptoms. And it reduces the pleasure of nicotine from cigarettes, by attaching firmly to the same parts of the brain that nicotine attaches to without stimulating them as strongly. With varenicline already in place, nicotine from a cigarette has fewer places to attach — it becomes harder to get a nicotine "buzz," which can make it easier to quit and stay quit.

How varenicline helps, step by step

1. When you smoke, nicotine activates cells in the brain's reward centre.

2. Nicotine attaches to receptors on brain cells, releasing dopamine, which makes you feel good.

3. When you stop smoking, the receptors are empty and less dopamine is released.

4. Varenicline blocks the nicotine receptors but still triggers some dopamine release, so you don't feel as bad. CDC illustrations.

Sources

• Centers for Disease Control and Prevention, "How Quit Smoking Medicines Work," Tips From Former Smokers. https://www.cdc.gov/tobacco/campaign/tips/quit-smoking/quit-smoking-medications/how-quit-smoking-medicines-work/index.html
• The film: CDC, "Nicotine Affects the Brain. Nicotine Replacement Therapy (NRT) Can Help You Quit Smoking," low-resolution video recovered from the Internet Archive's copy of https://www.cdc.gov/tobacco/campaign/tips/videos/tips-nicotine-and-nrt-lowres-video.mp4