Until two years ago, only two classes of smoking cessation drugs were available: nicotine replacement therapy (NRT) with multiple delivery methods (gum, patch, inhaler, spray, lozenge) and the mild antidepressant bupropion. All approximately double the rate of cessation when compared to placebo. Chantix (Varenicline) is the first new agent for smoking cessation approved in almost a decade and represents a third class of drug with a different mechanism of action than either nicotine replacement therapy or bupropion.
Studies done to date demonstrate that Chantix is associated with higher smoking cessation rates than placebo and produces better cessation rates than bupropion.
Chantix is a partial agonist that binds to a specific nicotinic receptor, resulting in a limited release of dopamine. Chantix also has a competitive antagonist effect on nicotine which blocks nicotine from binding to the receptors. These receptors play a principal role in mediating reinforcement and dependence producing effects of nicotine. The urge to smoke is therefore significantly reduced.
Chantix is suggested for anyone who currently smokes cigarettes. Treatment should be initiated one week before the target quit date. The recommended dose is 1mg twice daily for 12 weeks including an initial week of titration (0.5mg each day for 3 days then 0.5mg twice daily for 4 days). For those who are successful in quitting smoking at the end of 12 weeks, an additional 12 weeks of treatment is recommended to reduce the chance of relapse. Patients who cannot tolerate side effects from Chantix (nausea, insomnia, abnormal dreams, headaches and flatulence are the most commonly reported side effects) can have the dose temporarily or permanently lowered, as Chantix is available in 1mg and 0.5mg tablets.
Currently, there are 5.5 million people on Chantix in this country alone and 6.5 million world-wide. This medication has no contraindications and very few untoward side effects. However, a troubling list of central nervous system related events have been reported by Chantix users, such as depression, aggressive behavior, sudden drowsiness, and, most ominously, suicidality. Even though these reports are very few in number, they have resulted in exceedingly negative press and patient and doctor fears.
In November, the Food and Drug Administration began investigating reports of psychiatric events such as suicidal thoughts associated with Chantix. That prompted Pfizer to update the drug's labeling that patients should be monitored for unusual behavior and patients with a history of mental illness who are considering taking Chantix should let their doctors know of their condition.
In mid-May, a report was released by an organization called the “Institute for Safe Medication Practices” (ISMP) which claimed to have safety concerns about Chantix. The report summarized the most frequent side effects reported from using Chantix. By far the most common was nausea, which was more than twice as common as any other reported symptom. It was also notable that among the most commonly reported adverse effects, many are also recognized nicotine withdrawal symptoms (symptoms known to occur during smoking cessation, particularly without any treatment medication), such as depression, insomnia, anxiety, and weight increase.
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