Safety Concerns and Side Effects of Chantix

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Chantix is a popular brand name of the medication varenicline, a smoking cessation aid. Chantix is produced by the pharmaceutical company Pfizer. This medication works by blocking the brain from the feel-good effects of nicotine, taking away the "pleasant" effects of smoking cigarettes.

Chantix is available by prescription only, so you must consult with a doctor in order to take it. It is taken in tablet form usually once or twice a day. It's important to note, however, that a number of serious concerns about the side effects of Chantix—that involve changes in mood and behavior—have surfaced.

How Chantix Works

When you smoke a cigarette, nicotine targets receptors in the brain that then produce dopamine, also known as the "feel-good" hormone. Dopamine produces pleasurable feelings, so people are likely to continue smoking to feel these effects.

Chantix works by targeting these same receptors in the brain, blocking nicotine and its effects. The idea is that if a person no longer feels the pleasurable sensations of smoking, they are less likely to continue smoking.

Chantix may also reduce the urge to smoke. It's recommended, however, that you combine Chantix usage with other methods of quitting smoking, such as attending a support group to quit.

According to the manufacturer's instructions, you begin taking Chantix one week before your quit date and continue taking it for a 12-week period, after which time you can discuss with your doctor if you feel you need an additional 12 weeks of treatment.

Common Side Effects of Chantix

The most common adverse side effects of Chantix include:

  • Abdominal pain
  • Abnormal dreams
  • Changes in appetite
  • Changes in the menstrual cycle
  • Constipation
  • Diarrhea
  • Dry mouth
  • Gas
  • Headache
  • Heartburn
  • Insomnia
  • Joint or muscle pain
  • Lack of energy
  • Nausea
  • Nightmares
  • Sleep disturbances
  • Unpleasant taste in the mouth
  • Vomiting

Though some of these symptoms may only last a short time, be sure to speak to your doctor if these symptoms are persistent—you may require a reduction in your dose.

Severe Side Effects

There are more severe side effects that people have experienced when taking Chantix. These include both physical and mental health effects.

If you experience these or any other severe side effects from Chantix, stop taking Chantix immediately and contact your doctor. If your doctor isn't readily available, seek immediate medical care such as in the emergency room.

Physical effects include:

  • Blisters in the mouth
  • Calf pain
  • Chest pain, pressure, or squeezing
  • Difficulty speaking
  • Dizziness
  • Drowsiness
  • Hoarseness
  • Loss of consciousness
  • Numbness of the arms or legs
  • Seizures
  • Cardiovascular events
  • Angioedema and Hypersensitivity Reactions
  • Pain in the arms, back, neck, jaw, or stomach
  • Rash
  • Red, swollen, blistering, or peeling skin
  • Seizures
  • Severe skin reactions (mucosal lesions)
  • Swelling in the eyes, arms, ankles, face, feet, gums, hands, legs, lips, neck, throat, or tongue
  • Trouble swallowing or breathing
  • Weakness in the arms or legs

Severe mental, behavioral, and emotional side effects have been reported by some people when taking Chantix. They include:

  • Aggression or agitation
  • Changes in behavior or thinking
  • Hostility
  • Depression or anxiety
  • Panic
  • Sleepwalking
  • Suicidal thoughts

If you are having suicidal thoughts, contact the National Suicide Prevention Lifeline at 1-800-273-8255 for support and assistance from a trained counselor. If you or a loved one are in immediate danger, call 911.

For more mental health resources, see our National Helpline Database.

Myocardial infarction and stroke have occurred in people who've taken Chantix; however, in most cases, people had pre-existing cardiovascular disease.

In cases of sleepwalking, people have reported performing harmful behavior to themselves, others, or property.

According to the Food and Drug Administration (FDA), other neuropsychiatric adverse events included changes in mood (depression and mania), hallucinations, delusions, psychosis, paranoia, homicidal ideation, and suicidal ideation or actions.

While some people already had these or other mental health considerations when taking Chantix, others developed them several weeks after they started taking Chantix. You may be more likely to develop worse mental health issues if you have pre-existing conditions.

If you, your loved ones, and/or caregivers notice these symptoms, talk to your doctor right away. While some people's symptoms went away after they stopped taking Chantix, others had a continuation of their symptoms.

Warnings and Interactions

It's recommended by the FDA that people reduce their alcohol consumption until they know how they're affected by Chantix.

Patients also should use caution when driving or operating machinery until they know how they react to Chantix.


Be sure to tell your doctor if you're currently taking any prescription or over-the-counter (OTC) medications before starting Chantix, especially if you're taking blood thinners (anticoagulants) like Coumadin or Jantoven (warfarin) or insulin.

Tell your doctor if you're taking other quit-smoking medications like Aplenzin, Forfivo, Wellbutrin, Zyban, or Contrave (bupropion) as well as any nicotine replacement therapies (NRT) such as gum, inhaler, lozenges, nasal spray, or skin patches.

If you're taking Elixophyllin, Theo-24, or Theocron (theophylline), tell your doctor. Your doctor may need to adjust dosages of your prescription or OTC medications, if possible, prior to you taking Chantix.

Talk to Your Healthcare Provider

If you experience any of these symptoms while taking Chantix, communicate closely with your doctor until the symptoms go away.

Before you start taking Chantix, talk to your doctor about your mental health history, for instance, if you've ever experienced depression or other mental health conditions. If you've experienced a worsening of mental health issues due to nicotine withdrawal, it's best to tell your doctor about this as well.

If you have cardiovascular disease or experience somnambulism, contact your doctor as Chantix should be immediately discontinued.

The Bottom Line

Both Chantix and Zyban are in a class of quit aids that alter brain chemistry, and that has the potential to cause serious side effects for some people. This is why they are prescription medicines. You should have a doctor involved in your care if you're using one of these medications.

That said, the fact that Chantix and Zyban are still on the market speaks to the good that these quit aids are doing. With a person dying a tobacco-related death every 8 seconds somewhere in the world, day in and day out, 365 days a year, we can safely say that tobacco use is the grand-daddy of all risks that smokers should be concerned with.

Tobacco is responsible for upwards of 5 million deaths worldwide each year. If current trends continue unchanged, estimates put death by tobacco at 8 million annually by 2030.

If you happen to be in the group of people who should not use Chantix or Zyban, there are many other products available to help you quit smoking.

The absolute best quit aid and one that is a mandatory ingredient for long-term success with smoking cessation is your determination to quit smoking. With it, any quit aid of your choosing will work. Without it, none will.

The quit-smoking toolbox gives you links to information and the support necessary to build a solid quit smoking program for yourself.

You can quit smoking. Believe in yourself and the sky is the limit.

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2 Sources
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  1. MedlinePlus. Varenicline. Last updated July 2021.

  2. New York State Smokers' Quitline. About Chantix.