Pharmaceutical Approval Update: Varenicline Tartrate (Chantix)
Manufacturer: Pfizer, New York, NY Indication: Varenicline is indicated as an aid in smoking cessation.
Drug Class: As the tartrate salt, varenicline is a white to off-white to slightly yellow solid powder with the chemical name of 7,8,9,10-tetrahydro-6,10-methano-6H-pyrazino [2,3-h][3]benzazepine, (2R,3R)-2,3-dihydroxybutanedioate (1:1). It is not a controlled substance.
Uniqueness of Drug: Varenicline binds at sites in the brain with a high affinity and selectivity at alpha4 beta2 neuronal nicotinic acetylcholine receptors. The efficacy of varenicline in smoking cessation is believed to be the result of its activity at a subtype of the nicotinic receptor, where its binding produces agonist activity while simultaneously preventing nicotine binding to alpha4 beta2 receptors. The drug may help patients in two ways: (1) by providing some nicotine effects to ease the withdrawal symptoms and (2) by blocking the effects of nicotine from cigarettes if patients resume smoking.
Precautions: Physiological changes resulting from smoking cessation, with or without treatment with varenicline, may alter the pharmacokinetics or pharmacodynamics of some drugs (e.g., generic theophylline, warfarin drug, insulin). As a result, an adjustment in the dosage of generic bupropion XL might be necessary.
Drug Interactions: On the basis of varenicline’s characteristics and clinical experience to date, no clinically meaningful pharmacokinetic drug interactions have been observed.
Adverse Drug Events: ADEs associated with varenicline at a rate greater than 5% and at twice the rate with placebo included nausea, sleep disturbance, constipation, flatulence, and vomiting. Nausea was generally described as mild or moderate and often transient; for some subjects, however, it persisted for several months.
The incidence of nausea was dose-dependent. Initial titration of the dose was beneficial in reducing nausea. Nausea was reported by approximately 30% of patients treated with varenicline 1 mg twice daily after an initial week of dose titration. With varenicline 0.5 mg twice daily, the incidence of nausea was 16% after the initial titration. Approximately 3% of subjects using varenicline 1 mg twice daily in studies involving 12 weeks of treatment stopped treatment prematurely because of nausea. For patients with intolerable nausea, a dose reduction should be considered.
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Dosage and Administration: Smoking-cessation therapies are more likely to succeed for patients who are motivated to stop smoking and who are provided with additional advice and support. Patients should be given appropriate educational materials and counseling to support their attempts to quit.
Patients should be encouraged to set a date to stop smoking, and they should begin varenicline therapy one week before this date. Varenicline should be taken after eating and with a full glass of water. The recommended dose is 1 mg twice daily after a one-week titration period, as follows:
- days one to three: 0.5 mg once daily
- days four to seven: 0.5 mg twice daily
- day eight to the end of treatment: 1 mg twice daily
For patients who cannot tolerate ADEs after taking vareni-cline, the dose can be reduced temporarily or permanently. Patients should use varenicline for 12 weeks. For patients who have successfully stopped smoking at the end of 12 weeks, an additional course of 12 weeks of treatment with varenicline is recommended to enhance the likelihood of long-term abstinence.
Patients who do not succeed in stopping smoking during 12 weeks of initial therapy or who relapse after treatment should be encouraged to try again after factors contributing to the failed attempt have been identified and addressed.
Commentary: Varenicline is designed to partially activate the nicotinic receptor and to reduce the severity of cravings and nicotine-withdrawal symptoms. If a person smokes a cigarette while receiving treatment, varenicline has the potential to diminish the sense of satisfaction associated with smoking. This may help to prevent the cycle of nicotine addiction.
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The advent of varenicline represents ground-breaking science, leading to the first prescription treatment aimed directly at smoking cessation in nearly a decade. Nicotine affects nearly every organ in the body. Smoking is responsible for approximately one in five deaths in the U.S. and costs the health care system about $167 billion annually.
