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Chantix Side Effects

Generic Name: varenicline

Note: This page contains information about the side effects of varenicline. Some of the dosage forms included on this document may not apply to the brand name Chantix.

Not all side effects for Chantix may be reported. You should always consult a doctor or healthcare professional for medical advice. Side effects can be reported to the FDA here.

For the Consumer

Applies to varenicline: oral tablet

In addition to its needed effects, some unwanted effects may be caused by varenicline (the active ingredient contained in Chantix). In the event that any of these side effects do occur, they may require medical attention.

You should check with your doctor immediately if any of these side effects occur when taking varenicline:

Less common
  • Difficult or labored breathing
  • hyperventilation
  • tightness in the chest
Incidence not known
  • Anger
  • anxiety
  • behavior changes
  • discouragement
  • feeling sad or empty
  • feelings of panic
  • irregular heartbeats
  • irritability
  • loss of interest or pleasure
  • mood swings
  • restlessness
  • seeing, hearing, or feeling things that are not there
  • thoughts of killing oneself

Some of the side effects that can occur with varenicline may not need medical attention. As your body adjusts to the medicine during treatment these side effects may go away. Your health care professional may also be able to tell you about ways to reduce or prevent some of these side effects. If any of the following side effects continue, are bothersome or if you have any questions about them, check with your health care professional:

More common
  • Abnormal dreams
  • bloated or full feeling
  • change in taste
  • difficulty having a bowel movement (stool)
  • dry mouth
  • excess air or gas in the stomach or intestines
  • general feeling of discomfort or illness
  • headache
  • lack or loss of strength
  • loss of taste
  • nausea
  • passing gas
  • stomach pain
  • trouble sleeping
  • unusual tiredness or weakness
Less common
  • Acid or sour stomach
  • belching
  • body aches or pain
  • chills
  • cough
  • decreased appetite
  • dizziness
  • ear congestion
  • fever
  • heartburn
  • increased appetite
  • indigestion
  • itching skin or rash
  • loss of appetite
  • loss of voice
  • nightmares
  • sleepiness or unusual drowsiness
  • sneezing or sore throat
  • stomach discomfort or upset
  • stuffy or runny nose
  • trouble concentrating
  • unusual drowsiness, dullness, or feeling of sluggishness
  • vomiting

For Healthcare Professionals

Applies to varenicline: oral tablet


Gastrointestinal (GI) side effects have frequently included nausea (7.2% to 40%), flatulence (6% to 9%), constipation (5% to 8.5%), upper abdominal pain (2% to 7.7%), dry mouth (4% to 6%), abdominal pain (5%), dyspepsia (5%), vomiting (1% to 5%), and GI reflux disease (1%). Diarrhea, gingivitis, dysphagia, enterocolitis, eructation, gastritis, GI hemorrhage, mouth ulceration, esophagitis, gastric ulcer, intestinal obstruction, acute pancreatitis, and gall bladder disease have been reported. At least one case of cholecystitis has also been reported, in addition to case of peritonitis and a case of hemorrhoids and rectal prolapse.[Ref]

The most common side effect associated with varenicline in clinical trials was nausea. Nausea was typically transient and described as mild or moderate in intensity; however, some patients experienced persistent nausea throughout treatment.[Ref]


A 63-year-old male with stable bipolar disorder experienced a manic episode coincident with varenicline (the active ingredient contained in Chantix) therapy. The patient was admitted to an inpatient psychiatric unit and met criteria for a manic episode. He began exhibiting manic symptoms one week after initiating therapy with varenicline 1 mg twice daily for smoking cessation. Varenicline was stopped upon admission. Within one week of admission, he was euthymic, without manic or psychotic symptoms.

A 42-year-old female with a 17-year history of schizophrenia experienced exacerbation of schizophrenia coincident with varenicline therapy. She had been prescribed varenicline 2 mg for 5-days to help her stop smoking. The patient's mother reported a 5-day psychotic episode that began with increased activity. After she was advised to discontinue varenicline, she had no further exacerbation.[Ref]

Psychiatric side effects have included insomnia (19%), abnormal dreams (9% to 13%), sleep disorder (2%), and nightmare (2%). Anxiety, depression, emotional disorder, irritability, restlessness, aggression, agitation, disorientation, dissociation, decreased libido, mood swings, abnormal thinking, bradyphrenia, euphoric mood, hallucination, psychotic disorder, suicidal ideation, and erratic behavior have also been reported. Depressed mood, agitation, changes in behavior, and suicide have been reported during postmarketing experience. At least one case of varenicline-induced manic episode has also been reported, in addition to a case of exacerbation of schizophrenia.[Ref]

Nervous system

Nervous system side effects have frequently included headaches (10.3% to 19%), dysgeusia (8%), fatigue, malaise, asthenia, somnolence, and lethargy. Attention disturbances, dizziness, sensory disturbance, amnesia, migraine, parosmia, psychomotor hyperactivity, restless legs syndrome, syncope, tremor, balance disorder, cerebrovascular accident, convulsion, dysarthria, facial palsy, mental impairment, multiple sclerosis, nystagmus, impairment of psychomotor skills, transient ischemic attack, visual field defect, and drowsiness have been reported.[Ref]

The New Zealand (NZ) Intensive Medicines Monitoring Programme (IMMP) identified a series of 13 reports of memory impairment in patients taking varenicline. This case series adds to cases of memory impairment reported by the Institute for Safe Medication Practices (ISMP) from FDA datasets who postulated that vasoconstriction or vasodilation could be the underlying mechanism.[Ref]


Respiratory side effects have frequently included influenza (3.2% to 5.8%), rhinorrhea, dyspnea, and upper respiratory tract disorder. Epistaxis, respiratory disorders, asthma, pleurisy, and pulmonary embolism have also been reported.[Ref]


Dermatologic side effects have frequently included rash and pruritus. Hyperhidrosis, acne, dermatitis, dry skin, eczema, erythema, psoriasis, urticaria, and photosensitivity reaction have also been reported.[Ref]


Metabolic side effects have frequently included increased or decreased appetite and anorexia. Hyperlipidemia, hypokalemia, hyperkalemia, hypoglycemia, and increased weight have also been reported.[Ref]


Hematologic side effects have included anemia, lymphadenopathy, leukocytosis, thrombocytopenia, and splenomegaly.[Ref]


Cardiovascular side effects have included angina pectoris, arrhythmia, bradycardia, ventricular extrasystoles, myocardial infarction, palpitations, tachycardia, atrial fibrillation, cardiac flutter, coronary artery disease, cor pulmonale, abnormal electrocardiogram, acute coronary syndrome, hypertension, hypotension, peripheral ischemia, and thrombosis.[Ref]


Endocrine side effects have included thyroid gland disorders and diabetes mellitus. At least one case of pituitary hemorrhage has also been reported.[Ref]


Ocular side effects have included conjunctivitis, dry eye, eye irritation, blurred vision, visual disturbance, eye pain, acquired night blindness, transient blindness, cataract subcapsular, ocular vascular disorder, photophobia, and vitreous floaters.[Ref]


Hypersensitivity side effects including seasonal allergy (2.6% to 5.9%) have been reported.[Ref]


Genitourinary side effects have included abnormal urine analysis, polyuria, nocturia, urine abnormality, urinary retention, menstrual disorder, erectile dysfunction, and sexual dysfunction. At least one case of ovarian hematoma has also been reported.[Ref]


Musculoskeletal side effects have included arthralgia, back pain, muscle cramp, musculoskeletal pain, myalgia, arthritis, osteoporosis, and myositis.[Ref]


Renal side effects have included nephrolithiasis, urethral syndrome, and acute renal failure. At least one case of elevated blood creatinine has also been reported.[Ref]


Immunologic side effects commonly reported have included nasopharyngitis (35.9% to 51%), bronchitis, sinusitis, fungal infection, and viral infection.[Ref]


Hepatic side effects including abnormal liver function tests have been reported.[Ref]


Other side effects have included tinnitus, vertigo, deafness, Meniere's disease, chest pain, influenza-like symptoms, edema, thirst, chest discomfort, chills, pyrexia, increased muscle enzyme, and hot flash. At least one case of feeling abnormal has been reported, in addition to a case of elevated aspartate aminotransferase, two cases of elevated alanine aminotransferase, and one case of elevated blood bilirubin.[Ref]


1. "Varenicline (Chantix) for tobacco dependence." Med Lett Drugs Ther 48(1241-1242) (2006): 66-8

2. Nakamura M, Oshima A, Fujimoto Y, Maruyama N, Ishibashi T, Reeves KR "Efficacy and tolerability of varenicline, an alpha4beta2 nicotinic acetylcholine receptor partial agonist, in a 12-week, randomized, placebo-controlled, dose-response study with 40-week follow-up for smoking cessation in Japanese smokers." Clin Ther 29 (2007): 1040-56

3. Potts LA, Garwood CL "Varenicline: the newest agent for smoking cessation." Am J Health Syst Pharm 64 (2007): 1381-4

4. "Product Information. Chantix (varenicline)." Pfizer U.S. Pharmaceuticals Group, New York, NY.

5. Freedman R "Exacerbation of schizophrenia by varenicline." Am J Psychiatry 164 (2007): 1269

6. Kohen I, Kremen N "Varenicline-induced manic episode in a patient with bipolar disorder." Am J Psychiatry 164 (2007): 1269-70

7. Tan M, Harrison-Woolrych M "Memory impairment associated with varenicline : a case series from the New Zealand Intensive Medicines Monitoring Programme." Eur J Clin Pharmacol 69 (2013): 1195-6

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