Safety Concerns and Side Effects of Chantix

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Chantix (varenicline) is a prescription smoking cessation aid. It is produced by the pharmaceutical company Pfizer. The medication works by blocking the brain from experiencing 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 since its FDA approval in 2006.

How Chantix Works

When you smoke a cigarette, nicotine targets receptors in your brain that then produce dopamine, the "feel-good" hormone. Dopamine produces pleasurable feelings, making people more likely to continue smoking in order to continue to feel these effects.

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

It's recommended, however, that when you take Chantix you also use other methods of quitting smoking, such as attending a support group.

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 that, you should discuss with your prescribing doctor whether an additional 12 weeks of treatment is necessary.

Common Side Effects of Chantix

The most common adverse side effects of Chantix include:

  • Abdominal pain
  • Changes in appetite
  • Changes in the menstrual cycle
  • Constipation or diarrhea
  • Dry mouth or unpleasant taste in the mouth
  • Gas
  • Headache
  • Heartburn
  • Insomnia
  • Joint or muscle pain
  • Lack of energy
  • Nausea or vomiting
  • Nightmares, abnormal dreams, or other sleep disturbances

Though some of these symptoms may only last a short time, be sure to speak to your prescribing doctor if they are persistent. A reduction in your dose may be necessary.

Severe Side Effects

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

If you experience severe side effects from Chantix, stop taking Chantix immediately and contact your prescribing doctor. If your doctor isn't readily available, go to the emergency room for immediate medical care.

Physical Side Effects

Serious physical effects include:

  • Cardiovascular events
  • Chest pain, pressure, or squeezing
  • Difficulty speaking
  • Dizziness
  • Drowsiness
  • Hoarseness
  • Loss of consciousness
  • Numbness or weakness of the arms or legs
  • Pain in the arms, back, calves, neck, jaw, or stomach
  • Seizures
  • Skin irritation
  • Swelling
  • Trouble swallowing

Several potential side effects involve skin irritation. This includes skin that is red, swollen, blistering, or peeling, blisters in the mouth, or rashes. Severe skin reactions such as mucosal legions have occurred as well as angioedema (swelling under the skin).

Some people also experience swelling in the eyes, arms, ankles, face, feet, gums, hands, legs, lips, neck, throat, or tongue.

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

Mental, Behavioral, and Emotional Side Effects

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

Other neuropsychiatric adverse events included psychosis, paranoia, homicidal ideation, and suicidal ideation or actions. While some people already had these or other mental health concerns when taking Chantix, others developed them several weeks after they started taking Chantix.

You may be more likely to develop adverse mental health effects from taking Chantix if you have pre-existing mental health conditions.

If you, your loved ones, or caregivers notice these symptoms, talk to a 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 that a person reduces their alcohol consumption while taking Chantix until they know how they're affected by the medication. People also should use caution when driving or operating machinery until they know how they react to Chantix.

Be sure to tell your prescribing 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.

You should also 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 nicotine 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 the dosage of your prescription or OTC medications, prior to taking Chantix.

Talk to a Healthcare Provider

If you experience any of these symptoms while taking Chantix, communicate closely with your prescribing doctor.

Before you start taking Chantix, talk to a healthcare provider 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 the doctor about this as well.

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

Both Chantix and Zyban are in a class of quit aids that alter brain chemistry. They have 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.

If you are unable to take Chantix or Zyban, there are many other products available to help you quit smoking.

Other Methods for Quitting

Nicotine replacement therapy (NRT) can be helpful for quitting smoking, especially for people who have trouble quitting cold turkey.

One review estimates that NRT can improve a person's odds of quitting smoking by 50% to 70%. It is not recommended that you take Chantix and use NRT products at the same time.

However, you may be able to use NRT to wean yourself off of smoking and then switch to using Chantix a week before your quit date. Be sure to talk to a doctor first.

You may also find it helpful to join a support group, use a quit smoking app, or sign up for a quit smoking text service to send you tips for dealing with cravings. Speaking with a therapist can also help; they can teach you healthy coping mechanisms to cope with difficult emotions or other situations that can trigger you to smoke.

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9 Sources
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  1. MedlinePlus. Varenicline.

  2. Herman AI, DeVito EE, Jensen KP, Sofuoglu M. Pharmacogenetics of nicotine addiction: Role of dopaminePharmacogenomics. 2014;15(2):221-234. doi:10.2217/pgs.13.246

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

  4. U.S. Food and Drug Administration. FDA drug safety communication: Chantix (varenicline) may increase the risk of certain cardiovascular adverse effects in patients with cardiovascular disease.

  5. Pfizer Labs. Chantix (varenicline) tablets.

  6. Savage RL, Zekarias A, Caduff-Janosa P. Varenicline and abnormal sleep related eventsSleep. 2015;38(5):833-837. doi:10.5665/sleep.4686

  7. Wadgave U, Nagesh L. Nicotine replacement therapy: An overviewInt J Health Sci (Qassim). 2016;10(3):425-435.

  8. Chang PH, Chiang CH, Ho WC, Wu PZ, Tsai JS, Guo FR. Combination therapy of varenicline with nicotine replacement therapy is better than varenicline alone: A systematic review and meta-analysis of randomized controlled trials. BMC Public Health. 2015;15(1). doi:10.1186/s12889-015-2055-0

  9. National Institutes of Health. How to stay smokefree.