What are the major side effects of varenicline (Chantix)?

Major Side Effects of Varenicline (Chantix)

The major side effects of varenicline include nausea (occurring in approximately one-third of patients), neuropsychiatric symptoms (including agitation, depressed mood, changes in behavior, and suicidal ideation), insomnia, abnormal dreams, headache, and rare but serious risks of seizures and cardiovascular events. 1

Common Side Effects

• Nausea is the most frequently reported adverse effect, affecting 30-40% of patients, though it is typically mild to moderate and often diminishes over time 1, 2
• Insomnia affects 14-15% of users and is generally milder than that experienced with bupropion 1, 2
• Abnormal or vivid dreams occur in 10-13% of patients 1, 2
• Headache is reported in approximately 14% of patients 1
• Constipation and gas are also commonly reported gastrointestinal side effects 3

Serious Side Effects

Neuropsychiatric Effects

• Post-marketing reports have indicated treatment-emergent incidence of agitation, depressed mood, changes in behavior, and suicidal ideation in patients taking varenicline 1
• The FDA has issued warnings about these possible adverse effects, requiring prescribers to monitor patients for neuropsychiatric symptoms 1
• The EAGLES trial (a large randomized controlled trial) found no significant increase in neuropsychiatric adverse events with varenicline compared to nicotine patches or placebo 1, 2
• Despite this evidence, if any neuropsychiatric symptoms occur, varenicline treatment should be discontinued immediately and the patient assessed 1

Seizure Risk

• Seizures are a rare but significant adverse effect of varenicline 1, 2, 3
• Patients with brain metastases or elevated seizure risk should avoid varenicline 1, 2
• If a seizure occurs during treatment, varenicline should be stopped immediately and medical attention sought 3

Cardiovascular Concerns

• Cardiovascular events have been a topic of concern, though recent systematic reviews and meta-analyses have not identified a significant link between varenicline and increased risk of serious cardiovascular adverse events 1, 2
• Patients should be instructed to notify healthcare providers of symptoms of new or worsening cardiovascular events 3

Special Precautions

Alcohol Interaction

• Varenicline may increase the effects of alcohol, leading to increased drunkenness, unusual or aggressive behavior, and memory blackouts 3
• Patients should decrease alcohol consumption until they know how varenicline affects their tolerance 3

Driving and Operating Machinery

• Caution is advised when driving or operating machinery until the patient knows how varenicline affects them 3
• Sleepiness, dizziness, and trouble concentrating may occur 3

Skin Reactions

• Serious skin reactions including Stevens-Johnson syndrome and erythema multiforme have been reported 3
• Patients should stop taking varenicline at the first sign of rash with mucosal lesions or skin reaction 3

Sleepwalking

• Varenicline can cause sleepwalking which may lead to harmful behavior 3
• Treatment should be discontinued if sleepwalking occurs 3

Discontinuation Rates

• Treatment discontinuation due to nausea occurs in approximately 3% of patients 1
• Overall, patients receiving varenicline are nearly 1.5 times more likely to discontinue treatment due to adverse effects compared to those on placebo 4
• Adverse effects experienced during varenicline treatment are associated with higher discontinuation rates, which can negatively impact smoking cessation success 4

Monitoring Recommendations

• Monitor for neuropsychiatric symptoms, especially in patients with a history of psychiatric illness 2
• Assess for cardiovascular symptoms in patients with pre-existing cardiovascular disease 2
• Evaluate for skin reactions, particularly rash with mucosal lesions 3
• Watch for signs of seizure activity, especially in high-risk patients 2, 3