"The US Food and Drug Administration (FDA) has changed the labeling on the smoking cessation drug varenicline (Chantix, Pfizer Inc) to reflect concerns that the drug may lower tolerance to alcohol and is linked to a rare risk for seizures"...
The following serious adverse reactions were reported in postmarketing experience and are discussed in greater detail in other sections of the labeling:
- Neuropsychiatric symptoms and suicidality [see BOXED WARNING and WARNINGS AND PRECAUTIONS]
- Seizures [see WARNINGS AND PRECAUTIONS]
- Interaction with Alcohol [see WARNINGS AND PRECAUTIONS]
- Accidental injury [see WARNINGS AND PRECAUTIONS]
- Cardiovascular Events [see WARNINGS AND PRECAUTIONS]
- Angioedema and hypersensitivity reactions [see WARNINGS AND PRECAUTIONS]
- Serious skin reactions [see WARNINGS AND PRECAUTIONS]
In the placebo-controlled studies, the most common adverse events associated with CHANTIX ( > 5% and twice the rate seen in placebo-treated patients) were nausea, abnormal (vivid, unusual, or strange) dreams, constipation, flatulence, and vomiting.
The treatment discontinuation rate due to adverse events in patients dosed with 1 mg twice daily was 12% for CHANTIX, compared to 10% for placebo in studies of three months' treatment. In this group, the discontinuation rates that are higher than placebo for the most common adverse events in CHANTIXtreated patients were as follows: nausea (3% vs. 0.5% for placebo), insomnia (1.2% vs. 1.1% for placebo), and abnormal dreams (0.3% vs. 0.2% for placebo).
Clinical Trials Experience
Because clinical trials are conducted under widely varying conditions, the adverse reactions rates observed in the clinical studies of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.
During the premarketing development of CHANTIX, over 4500 subjects were exposed to CHANTIX, with over 450 treated for at least 24 weeks and approximately 100 for a year. Most study participants were treated for 12 weeks or less.
The most common adverse event associated with CHANTIX treatment is nausea, occurring in 30% of patients treated at the recommended dose, compared with 10% in patients taking a comparable placebo regimen [see WARNINGS AND PRECAUTIONS].
Table 5 shows the adverse events for CHANTIX and placebo in the 12- week fixed dose studies with titration in the first week [Studies 2 (titrated arm only), 4, and 5]. Adverse events were categorized using the Medical Dictionary for Regulatory Activities (MedDRA, Version 7.1).
MedDRA High Level Group Terms (HLGT) reported in ≥ 5% of patients in the CHANTIX 1 mg twice daily dose group, and more commonly than in the placebo group, are listed, along with subordinate Preferred Terms (PT) reported in ≥ 1% of CHANTIX patients (and at least 0.5% more frequent than placebo). Closely related Preferred Terms such as 'Insomnia', 'Initial insomnia', 'Middle insomnia', 'Early morning awakening' were grouped, but individual patients reporting two or more grouped events are only counted once.
Table 5: Common Treatment Emergent AEs (%) in the Fixed-Dose,
Placebo-Controlled Studies (HLGTs > 5% of patients in the 1 mg BID CHANTIX
Group and more commonly than placebo and PT ≥ 1% in the 1 mg BID CHANTIX
Group, and 1 mg BID CHANTIX at least 0.5% more than Placebo)
|SYSTEM ORGAN CLASS High Level Group Term Preferred Term||CHANTIX 0.5 mg BID
|CHANTIX 1 mg BID
|GI Signs and Symptoms|
|Abdominal Pain *||5||7||5|
|GI Motility/Defecation Conditions|
|Gastroesophageal reflux disease||1||1||0|
|Salivary Gland Conditions|
|General Disorders NEC|
|Respiratory Disorders NEC|
|Upper Respiratory Tract Disorder||7||5||4|
|Epidermal and Dermal Conditions|
|METABOLISM & NUTRITION|
|* Includes PTs Abdominal (pain, pain upper, pain lower,
discomfort, tenderness, distension) and Stomach discomfort
** Includes PTs Insomnia/Initial insomnia/Middle insomnia/Early morning awakening
The overall pattern and frequency of adverse events during the longerterm trials was similar to those described in Table 5, though several of the most common events were reported by a greater proportion of patients with long-term use (e.g., nausea was reported in 40% of patients treated with CHANTIX 1 mg twice daily in a one-year study, compared to 8% of placebo-treated patients).
Following is a list of treatment-emergent adverse events reported by patients treated with CHANTIX during all clinical trials. The listing does not include those events already listed in the previous tables or elsewhere in labeling, those events for which a drug cause was remote, those events which were so general as to be uninformative, and those events reported only once which did not have a substantial probability of being acutely life-threatening.
Blood and Lymphatic System Disorders. Infrequent: anemia, lymphadenopathy. Rare: leukocytosis, splenomegaly, thrombocytopenia. Cardiac Disorders. Infrequent: angina pectoris, arrhythmia, bradycardia, myocardial infarction, palpitations, tachycardia, ventricular extrasystoles. Rare: acute coronary syndrome, atrial fibrillation, cardiac flutter, cor pulmonale, coronary artery disease.
Endocrine Disorders. Infrequent: thyroid gland disorders.
Eye Disorders. Infrequent: conjunctivitis, dry eye, eye irritation, eye pain, vision blurred, visual disturbance. Rare: acquired night blindness, blindness transient, cataract subcapsular, ocular vascular disorder, photophobia, vitreous floaters.
Gastrointestinal Disorders. Frequent: diarrhea. Infrequent: dysphagia, enterocolitis, eructation, esophagitis, gastritis, gastrointestinal hemorrhage, mouth ulceration. Rare: gastric ulcer, intestinal obstruction, pancreatitis acute.
General Disorders and Administration Site Conditions. Frequent: chest pain, edema, influenza-like illness. Infrequent: chest discomfort, chills, pyrexia.
Hepatobiliary Disorders. Infrequent: gall bladder disorder.
Investigations. Frequent: liver function test abnormal, weight increased. Infrequent: electrocardiogram abnormal, muscle enzyme increased, urine analysis abnormal.
Nervous System Disorders. Frequent: disturbance in attention, dizziness, sensory disturbance. Infrequent: amnesia, migraine, parosmia, psychomotor hyperactivity, restless legs syndrome, syncope, tremor. Rare: balance disorder, cerebrovascular accident, convulsion, dysarthria, facial palsy, mental impairment, multiple sclerosis, nystagmus, psychomotor skills impaired, transient ischemic attack, visual field defect.
Reproductive System and Breast Disorders. Rare: sexual dysfunction. Frequent: menstrual disorder. Infrequent: erectile dysfunction.
Vascular Disorders. Frequent: hot flush. Infrequent: thrombosis.
CHANTIX has also been studied in postmarketing trials including (1) a trial conducted in patients with chronic obstructive pulmonary disease (COPD), (2) a trial conducted in generally healthy patients (similar to those in the premarketing studies) in which they were allowed to select a quit date between days 8 and 35 of treatment (“alternative quit date instruction trial”), (3) a trial conducted in patients with stable cardiovascular disease and (4) a trial conducted in patients with stable schizophrenia or schizoaffective disorder.
Adverse events in the trial of patients with COPD and in the alternative quit date instruction trial were quantitatively and qualitatively similar to those observed in premarketing studies.
In the trial of patients with stable cardiovascular disease, more types and a greater number of cardiovascular events were reported compared to premarketing studies. Treatment-emergent (on-treatment or 30 days after treatment) cardiovascular events reported with a frequency ≥ 1% in either treatment group in this study were angina pectoris (3.7% and 2.0% for varenicline and placebo, respectively), chest pain (2.5% vs. 2.3%), peripheral edema (2.0% vs. 1.1%), hypertension (1.4% vs. 2.6%), and palpitations (0.6 % vs. 1.1%). Deaths and serious cardiovascular events occurring over the 52 weeks of the study (treatment emergent and non-treatment emergent) were adjudicated by a blinded, independent committee. The following treatmentemergent adjudicated events occurred with a frequency ≥ 1% in either treatment group: nonfatal MI (1.1% vs. 0.3% for varenicline and placebo, respectively), and hospitalization for angina pectoris (0.6% vs. 1.1%). During non-treatment follow up to 52 weeks, the adjudicated events included need for coronary revascularization (2.0% vs. 0.6%), hospitalization for angina pectoris (1.7% vs. 1.1%), and new diagnosis of peripheral vascular disease (PVD) or admission for a PVD procedure (1.4% vs. 0.6%). Some of the patients requiring coronary revascularization underwent the procedure as part of management of nonfatal MI and hospitalization for angina. Cardiovascular death occurred in 0.3% of patients in the varenicline arm and 0.6% of patients in the placebo arm over the course of the 52-week study.
In the trial of patients with stable schizophrenia or schizoaffective disorder, 128 smokers on antipsychotic medication were randomized 2:1 to varenicline (1 mg twice daily) or placebo for 12 weeks with 12-week non-drug follow-up. The most common adverse events in patients taking varenicline were nausea (24% vs. 14.0% on placebo), headache (11% vs. 19% on placebo) and vomiting (11% vs. 9% on placebo). Among reported neuropsychiatric adverse events, insomnia was the only event that occurred in either treatment group in ≥ 5% of subjects at a rate higher in the varenicline group than in placebo (10% vs. 5%). These common and neuropsychiatric adverse events occurred on treatment or within 30 days after the last dose of study drug. There was no consistent worsening of schizophrenia in either treatment group as measured by the Positive and Negative Syndrome Scale. There were no overall changes in extra-pyramidal signs, as measured by the Simpson-Angus Rating Scale. The Columbia-Suicide Severity Rating Scale was administered at baseline and at clinic visits during the treatment and non-treatment follow-up phases. Over half of the patients had a lifetime history of suicidal behavior and/or ideation (62% on varenicline vs. 51% on placebo), but at baseline, no patients in the varenicline group reported suicidal behavior and/or ideation vs. one patient in the placebo group (2%). Suicidal behavior and/or ideation were reported in 11% of the varenicline-treated and 9% of the placebo-treated patients during the treatment phase. During the post-treatment phase, suicidal behavior and/or ideation were reported in 11% of patients in the varenicline group and 5% of patients in the placebo group. Many of the patients reporting suicidal behavior and ideation in the follow-up phase had not reported such experiences in the treatment phase. However, no new suicidal ideation or behavior emerged in either treatment group shortly (within one week) after treatment discontinuation (a phenomenon noted in post-marketing reporting). There were no completed suicides. There was one suicide attempt in a varenicline-treated patient. The limited data available from this single smoking cessation study are not sufficient to allow conclusions to be drawn.
The following adverse events have been reported during post-approval use of CHANTIX. Because these events are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
There have been reports of depression, mania, psychosis, hallucinations, paranoia, delusions, homicidal ideation, aggression, hostility, anxiety, and panic, as well as suicidal ideation, suicide attempt, and completed suicide in patients attempting to quit smoking while taking CHANTIX [see BOXED WARNING, WARNINGS AND PRECAUTIONS]. Smoking cessation with or without treatment is associated with nicotine withdrawal symptoms and the exacerbation of underlying psychiatric illness. Not all patients had known pre-existing psychiatric illness and not all had discontinued smoking.
There have been post-marketing reports of new or worsening seizures in patients treated with CHANTIX [see WARNINGS AND PRECAUTIONS].
There have been post-marketing reports of patients experiencing increased intoxicating effects of alcohol while taking CHANTIX. Some reported neuropsychiatric events, including unusual and sometimes aggressive behavior [see WARNINGS AND PRECAUTIONS].
There have been reports of hypersensitivity reactions, including angioedema [see WARNINGS AND PRECAUTIONS].
There have been reports of myocardial infarction (MI) and cerebrovascular accident (CVA) including ischemic and hemorrhagic events in patients taking Chantix. In the majority of the reported cases, patients had preexisting cardiovascular disease and/or other risk factors. Although smoking is a risk factor for MI and CVA, based on temporal relationship between medication use and events, a contributory role of varenicline cannot be ruled out.
Read the Chantix (varenicline) Side Effects Center for a complete guide to possible side effects
Based on varenicline characteristics and clinical experience to date, CHANTIX has no clinically meaningful pharmacokinetic drug interactions [see CLINICAL PHARMACOLOGY].
Use With Other Drugs For Smoking Cessation
Safety and efficacy of CHANTIX in combination with other smoking cessation therapies have not been studied.
Bupropion: Varenicline (1 mg twice daily) did not alter the steady-state pharmacokinetics of bupropion (150 mg twice daily) in 46 smokers. The safety of the combination of bupropion and varenicline has not been established.
Nicotine replacement therapy (NRT): Although co-administration of varenicline (1 mg twice daily) and transdermal nicotine (21 mg/day) for up to 12 days did not affect nicotine pharmacokinetics, the incidence of nausea, headache, vomiting, dizziness, dyspepsia, and fatigue was greater for the combination than for NRT alone. In this study, eight of twenty-two (36%) patients treated with the combination of varenicline and NRT prematurely discontinued treatment due to adverse events, compared to 1 of 17 (6%) of patients treated with NRT and placebo.
Effect Of Smoking Cessation On Other Drugs
Physiological changes resulting from smoking cessation, with or without treatment with CHANTIX, may alter the pharmacokinetics or pharmacodynamics of certain drugs (e.g., theophylline, warfarin, insulin) for which dosage adjustment may be necessary.
Drug Abuse And Dependence
Varenicline is not a controlled substance.
Fewer than 1 out of 1000 patients reported euphoria in clinical trials with CHANTIX. At higher doses (greater than 2 mg), CHANTIX produced more frequent reports of gastrointestinal disturbances such as nausea and vomiting. There is no evidence of dose-escalation to maintain therapeutic effects in clinical studies, which suggests that tolerance does not develop. Abrupt discontinuation of CHANTIX was associated with an increase in irritability and sleep disturbances in up to 3% of patients. This suggests that, in some patients, varenicline may produce mild physical dependence which is not associated with addiction.
In a human laboratory abuse liability study, a single oral dose of 1 mg varenicline did not produce any significant positive or negative subjective responses in smokers. In non-smokers, 1 mg varenicline produced an increase in some positive subjective effects, but this was accompanied by an increase in negative adverse effects, especially nausea. A single oral dose of 3 mg varenicline uniformly produced unpleasant subjective responses in both smokers and non-smokers.
Studies in rodents have shown that varenicline produces behavioral responses similar to those produced by nicotine. In rats trained to discriminate nicotine from saline, varenicline produced full generalization to the nicotine cue. In self-administration studies, the degree to which varenicline substitutes for nicotine is dependent upon the requirement of the task. Rats trained to self-administer nicotine under easy conditions continued to selfadminister varenicline to a degree comparable to that of nicotine; however in a more demanding task, rats self-administered varenicline to a lesser extent than nicotine. Varenicline pretreatment also reduced nicotine self-administration.
Read the Chantix Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 10/3/2014
This monograph has been modified to include the generic and brand name in many instances.
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