Varenicline may cause side effects, some of which are common and others potentially serious. It’s important to speak to your doctor if symptoms are severe or persistent.
Common side effects include:
- Nausea (the most common side effect and may affect up to 30% of users)
- Constipation
- Diarrhea
- Gas
- Abdominal pain
- Vomiting
- Heartburn (acid reflux)
- Bad taste in the mouth
- Dry mouth
- Changed appetite (increased or decreased)
- Toothache
- Trouble sleeping (insomnia), unusual dreams, or nightmares
- Headache
- Lack of energy or tiredness
- Back, joint, or muscle pain
- Sore or swollen nose or throat
- Abnormal menstrual cycles
Tips such as hydrating, dietary changes, and using over-the-counter remedies may help manage some mild side effects.[1][2][4][5]
Serious side effects (seek immediate medical attention if any occur):
- Swelling of the face, throat, tongue, lips, gums, eyes, neck, hands, arms, feet, or lower legs
- Hoarseness or difficulty swallowing or breathing
- Rash, blistering, peeling, or sores in the mouth
- Chest pain, pressure, discomfort in arms, back, neck, jaw, or stomach
- Shortness of breath or sweating, especially with chest pain
- Speech difficulties or sudden numbness/weakness
- Calf pain while walking
- Seizures, muscle twitching, spasms, or tremors
- Sleepwalking
- Mental health changes: agitation, aggression, hostility, confusion, depressed mood, or suicidal thoughts or behaviors
Serious allergic reactions such as swelling, hives, and breathing difficulties can occur and require emergency care.[1][2][3][5][6]
Rare side effects:
- Vision changes (difficulty seeing at night, increased sensitivity to light, seeing floating spots)
- Unusual bleeding or bruising
- Rapid or unexplained weight changes
- Unusual drowsiness or sluggishness
If you notice any unusual or concerning symptoms while taking varenicline, notify your doctor. Some symptoms may be due to nicotine withdrawal rather than the medication itself. Mental health side effects tend to occur more often in people with a prior history of psychiatric illness.[3][5]