Reviewed on 1/10/2022

Generic Name: Varenicline

Brand Name: Chantix 

Drug Class: Smoking Cessation Aids

What Is Varenicline and How Does It Work?

Varenicline is a prescription medication used as an aid to smoking cessation.

  • Varenicline is available under the following different brand names: Chantix.

What Are Dosages of Varenicline?

Adult dosage


  • 0.5mg
  • 1mg

Smoking Cessation

Adult dosage

  • Initiate regimen 1 week before quit smoking date
  • Days 1-3: 0.5mg orally once daily
  • Days 4-7: 0.5mg orally twice daily
  • Day 8 to end of treatment: 1mg orally twice daily
  • If quitting is successful after 12 weeks, continue another 12 weeks at 1 mg every 12 hours

Dosage Considerations – Should be Given as Follows: 

  1. See "Dosages."

What Are Side Effects Associated with Using Varenicline?

Common side effects of Varenicline include:

Serious side effects of Varenicline include:

Rare side effects of Varenicline include:

  • none 
This is not a complete list of side effects and other serious side effects or health problems may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.


What is the average weight gain for those who quit smoking? See Answer

What Other Drugs Interact with Varenicline?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

  • Varenicline has severe interactions with no other drugs.
  • Varenicline has serious interactions with the following drugs:
    • tafenoquine 
    • trilaciclib 
  • Varenicline has moderate interactions with the following drugs:
  • Varenicline has minor interactions with the following drugs:

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this drug, tell your doctor or pharmacist of all the drugs you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Varenicline?


  • Documented hypersensitivity or skin reactions to drug or components of formulation
  • Nonsmokers 

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Varenicline?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Varenicline?”


  • May cause nausea; reduce dose if nausea occurs
  • Somnambulism reported, including cases describing harmful behavior to self, others, or property; instruct patients to discontinue varenicline and notify their healthcare professional
  • Seizures reported; some patients had no history of seizures, whereas others had a history of seizure disorder that was remote or well-controlled; in most cases, the seizure occurred within the first month of therapy; use with caution in patients with history of seizures or with other factors that might lower seizure threshold
  • May cause CNS depression; use caution when performing tasks requiring mental alertness, such as, operating heavy machinery or driving
  • Hypersensitivity reactions reported, including angioedema
  • Rare but serious skin reactions reported, including Stevens-Johnson Syndrome and erythema multiforme
  • Neuropsychiatric adverse effects
    • Serious neuropsychiatric adverse events reported; these postmarketing reports include changes in mood (including depression and mania), psychosis, hallucinations, paranoia, delusions, homicidal ideation, aggression, hostility, agitation, anxiety, and panic, as well as suicidal ideation, suicide attempt, and completed suicide
    • Some patients who stopped smoking may have been experiencing symptoms of nicotine withdrawal, including depressed mood
    • Depression, rarely including suicidal ideation, has been reported in smokers undergoing a smoking cessation attempt without medication; however, some of these adverse events occurred in patients taking varenicline who continued to smoke
    • Neuropsychiatric adverse events occurred in patients without and with pre-existing psychiatric disease; some patients experienced worsening of their psychiatric illnesses
    • Some neuropsychiatric adverse events, including unusual and sometimes aggressive behavior directed to oneself or others, may have been worsened by concomitant use of alcohol
    • Advise patients and caregivers that the patient should stop taking varenicline and contact a healthcare provider immediately if agitation, depressed mood, or changes in behavior or thinking that are not typical are observed, or if the patient develops suicidal ideation or suicidal behavior
  • Alcohol interaction
    • Patients should reduce amount alcohol they consume when initiating therapy until they know whether it increases intoxicating effects
    • Postmarketing reports of patients experiencing increased intoxicating effects of alcohol while taking varenicline; some cases described unusual and sometimes aggressive behavior, and were often accompanied by amnesia for the events
  • Cardiovascular risk

Pregnancy and Lactation

  • Available data have not suggested increased risk for major birth defects following exposure to varenicline in pregnancy, compared with women who smoke; smoking during pregnancy causes increased risks of orofacial clefts, premature rupture of membranes, placenta previa, placental abruption, ectopic pregnancy, fetal growth restriction and low birth weight, stillbirth, preterm delivery and shortened gestation, neonatal death, sudden infant death syndrome and reduction of lung function in infants; it is not known whether quitting smoking with varenicline during pregnancy reduces these risks
  • Because there is no data on the presence of varenicline in human milk and effects on breastfed infants, breastfeeding women should monitor their infant for seizures and excessive vomiting, which are adverse reactions that have occurred in adults that may be clinically relevant in breastfeeding infants.
Medscape. Chantix.

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