Chantix (Varenicline) Side Effects
Nausea is the most common side effect of varenicline (Chantix), occurring in 30-40% of users, while other common side effects include insomnia, abnormal dreams, and headache. 1
Common Side Effects
- Nausea (30-40% of users) - typically mild to moderate, diminishes over time 1, 2
- Insomnia (14-15%) 1, 2
- Abnormal or vivid dreams (10-13%) 1, 3
- Headache (14%) 2, 4
- Constipation 3
- Gas 3
- Vomiting 3
Serious Side Effects
Neuropsychiatric Effects
Risk of neuropsychiatric symptoms requiring monitoring:
A large randomized controlled trial (EAGLES trial) examined neuropsychiatric safety in patients with and without psychiatric disorders and found no significant increase in neuropsychiatric adverse events with varenicline compared to nicotine patches or placebo 1
Other Serious Side Effects
- Seizures - rare but significant risk, especially in patients with brain metastases 1
- Cardiovascular events - some studies have indicated a small but significant increased risk 1
- Somnambulism (sleepwalking) - can sometimes lead to harmful behavior 3
- Serious skin reactions including Stevens-Johnson syndrome and erythema multiforme 3
- Angioedema - swelling of face, mouth, and neck that can lead to respiratory compromise 3
Contraindications
- Brain metastases (due to seizure risk) 1
- History of serious allergic or skin reactions to varenicline 3
Precautions and Monitoring
- Patients should be monitored for development or worsening of neuropsychiatric symptoms, especially those with a history of psychiatric illness 1
- Patients should be advised to use caution when driving or operating machinery until they know how varenicline affects them 3
- Patients should be advised to decrease alcohol consumption during treatment with varenicline 3
- Healthcare providers should weigh the benefits of smoking cessation against the potential risks of neuropsychiatric side effects 1
Discontinuation Due to Side Effects
- Adverse effects are associated with higher rates of discontinuation (OR = 1.47 [1.19; 1.81]) compared to placebo 2
- Nausea is associated with discontinuation rates between 0.6% and 7.6% 6
Special Considerations
- Nausea may need to be managed carefully in patients with cancer, especially during chemotherapy 1
- Dose adjustments may be considered if clinically indicated to manage side effects 1
- Starting with a lower dose and titrating up can help minimize nausea 4
- Patients and caregivers should be alerted to monitor for and report neuropsychiatric symptoms immediately 6
Despite these side effects, guidelines indicate that in most circumstances, the side effects related to smoking cessation medications are minimal and are considered an acceptable risk compared to continued smoking, with serious side effects being extremely rare 1.