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New Drug for Smoking Cessation: Chantix Added to Formulary

The FDA states that "Tobacco use, particularly cigarette smoking, is the single most preventable cause of death in the United States and is responsible for a growing list of cancers as well as chronic diseases including those of the lung and heart." Smoking remains the leading preventable cause of illness and premature death in the United States and claims approximately 438,000 lives per year. Approximately forty-one percent of smokers will actually try to quit, but they usually relapse. Approximately ten percent of smokers will truly quit and maintain abstinence.

There are currently seven approved therapies for smoking cessation. Older agents include a variety of nicotine replacement products (gum, patches, nasal spray, inhalers and lozenges) and Bupropion SR. Bupropion is an aminoketone antidepressant that is thought to inhibit dopamine reuptake in the mesolimbic dopamine system, or the reward center, of the brain.

Chantix® (varenicline), a partial agonist at the alpha-4 beta-2 nicotinic acetylcholine receptor, is the newest addition to the tobacco cessation arsenal. It relieves cravings and withdrawal symptoms of nicotine through agonist actions. In addition, it blocks the reinforcing effects of continued nicotine use via its antagonist action. Thus, the patient who continues to smoke while taking varenicline receives no satisfaction from his actions. Maximum plasma concentrations occur in approximately three to four hours after taking the drug orally. Oral bioavailability is unaffected by food or time of day. The half-life of varenicline is approximately twenty-four hours, with ninety-two percent of the drug being excreted by the kidney.

Studies were performed with concomitant administration of digoxin, warfarin, transdermal nicotine, bupropion, cimetidine, and metformin. The results displayed no clinically significant interactions. When taken with cimetidine, varenicline levels were increased by twenty-nine percent. It has been mentioned that there could be potential interactions in patients taking insulin, asthma meds, or anti-coagulants. Common adverse effects include nausea (as high as thirty percent in clinical trials), vomiting, insomnia, constipation and flatulence. Varenicline is a pregnancy category C drug; it is unknown whether it is excreted into breast milk or harmful during labor/delivery.

Chantix® is available in two strengths: 0.5mg and 1mg tablets. When using varenicline, patients should set a quit date with medication starting approximately one week prior to that date. The typical dose to minimize side effects is as follows: 0.5mg po daily for three days, 0.5mg po twice daily for four days, and 1mg po daily twice daily there-after for twelve to twenty-four weeks. There is no renal dosing adjustment in patients with mild renal dysfunction; however 0.5mg po twice daily is the maximum dosage for those with severe renal dysfunction. Patients receiving dialysis should receive no more than 0.5mg po daily. Varenicline has not been studied in children; therefore, the safety and efficacy in these has not been established.

Varenicline has been studied in numerous clinical trials, with comparisons to both bupropion SR and placebo. Of note, patients in these trials all had active weekly smoking cessation counseling. Patients were given twelve weeks of treatment with either varenicline, bupropion SR, or placebo, and were monitored for an additional forty weeks. In one study, patients who had been successful after twelve weeks of therapy were continued on varenicline for an additional twelve weeks (the bupropion SR group was continued on placebo). All studies displayed positive trends in favor of varenicline. After one year, there was no difference between cessation rates in patients taking bupropion SR or varenicline for twelve weeks. In contrast, there was a statistical difference in cessation rates after one year if patients who had been successful with twelve weeks of varenicline therapy were continued for an additional twelve weeks. This begs the question whether patients would do better with longer treatment courses of bupropion SR as well.

The entry of this drug onto the market is very exciting for healthcare providers as well as patients who are weighing their smoking cessation options. There is no "magic pill" for smoking cessation; however, medications such as varenicline may assist with cessation. Varenicline offers another option from which patients and healthcare providers may choose to assist with smoking cessation.