When most smokers try to quit smoking, they often use nicotine gum, lozenges, and patches, which have been popular choices since the 1980s.

In a previous article, I discussed the recent rise of e-cigarettes, which like those older products are intended to deliver nicotine into the user's bloodstream without the cancer-causing tobacco smoke.

However, nicotine isn't completely safe either -- it can cause high blood pressure and an elevated heart rate, leading to other cardiovascular problems.

Source: Wikimedia.

That's where smoking-cessation drugs, such as Pfizer's (NYSE:PFE) Chantix/Champix and GlaxoSmithKline's (NYSE:GSK) Zyban, come in. These drugs attempt to help smokers quit smoking without the use of nicotine. Meanwhile, anti-obesity drugs such as Belviq from Arena Pharmaceuticals (NASDAQ:ARNA) and Eisai (OTC:ESALY) have also shown potential in curbing nicotine cravings.

Let's take a closer look at three key things you need to know about these drugs, and if they should be considered viable alternatives to traditional smoking cessation products.

1. How Chantix works
The FDA approved Chantix in 2006. The drug prevents nicotine from reaching the brain's receptors, thus decreasing the amount of pleasure-causing dopamine to be released into the bloodstream. In other words, the brain no longer rewards you for smoking.

However, this approach has been controversial -- the drug has been known to cause severe mood swings, depression, and suicidal thoughts in some patients. Between 2009 and 2013, 544 suicides and 1,869 attempted suicides related to Chantix were recorded by the FDA as "adverse events." An FDA study in 2011, however, concluded that Chantix was not "directly linked" to psychiatric problems, despite groups such as the Federal Aviation Administration banning employees from taking the drug.

Chantix hit peak sales of $883 million in 2007. In 2012, that figure had dropped to $670 million, accounting for only 1% of Pfizer's top line. Analysts had originally expected Chantix to hit peak sales north of $900 million.

2. How Zyban and its generic competitors work
The FDA approved Zyban (also known in a higher dose as Wellbutrin) in 1997. Generic versions (bupropion) from Actavis, Mylan, Impax, and other companies were approved starting in 2004.

Zyban is an antidepressant that prevents two neurotransmitters, noradrenaline and dopamine, from being reabsorbed by nerve cells in the brain. This increases the amount of available free noradrenaline and dopamine in the brain, which theoretically leads to a lower desire to smoke.

Like Chantix, Zyban is also known to cause mood swings and suicidal thoughts, for which both drugs carry a black box warning.

GSK also notably doesn't consider Pfizer's Chantix to be a direct competitor. Instead, it lists common antidepressants, such as Eli Lilly's Cymbalta, Pfizer's Effexor, and Forest Labs' Lexapro, as its main competition.

Since Zyban has faced generic competition over the past decade, it only generated $139 million in sales in 2012, accounting for 0.3% of GSK's total revenue. GlaxoSmithKline markets two version of the drug -- Wellbutrin SR (sustained release) and Wellbutrin XL (extended release).

The Mayo Clinic is conducting a study combining Chantix and generic bupropion into a single treatment. The study has shown higher smoking abstinence rates at 12 weeks (53% vs. 43.2%) and 26 weeks (36.6% vs. 27.6%) after the administration of both drugs compared to the use of Chantix alone.

3. Is Arena's Belviq the next smoking cessation drug?
Meanwhile, Arena Pharmaceuticals, which has been struggling with weak sales of Belviq, plans to start a phase 2 trial testing the obesity drug for smoking cessation later this year.

Arena, which is partnered with Eisai in the global marketing of Belviq, is starting the trial based on tests that demonstrated the drug reduced the desire for nicotine in animals. Belviq, like Chantix and Zyban, also shares a similar trait with antidepressants -- it stimulates the neurotransmitter serotonin, which can affect a person's mood and appetite.

Although the idea of a combination weight loss and smoking cessation pill might sound lucrative, investors should remember that Belviq has only generated $3 million in sales (which accounts for 31.5% of Eisai's sales of $9.5 million) since being launched in the second quarter of fiscal 2013. That sluggish start makes analysts' peak estimates of $1 billion look far too lofty.

Therefore, it's likely that Arena is just trying to generate some investor interest in the drug, considering the rising media interest in e-cigarettes and smoking cessation products.

The Foolish takeaway
In conclusion, here are four things to remember when comparing smoking cessation drugs to other nicotine products:

  • They are related to antidepressants, which have also been used to treat sleep disorders, ADHD, and other problems.

  • Replacing cigarettes with antidepressants might just replace one problem with another.

  • The psychological side effects of smoking-cessation drugs should be carefully weighed against the physical side effects of nicotine.

  • E-cigarettes appear to be a more effective psychological and physical replacement for cigarettes, thanks to their liquid nicotine vapor and lighted LED tips.

Yet despite these issues, all of these products could help decrease the rate of smoking in the United States, which was the leading cause of nearly 160,000 lung cancer deaths in 2013.

What do you think about these alternatives to smoking? Please share your thoughts in the comments section below!