What is the most common side effect of varenicline?

Varenicline is a medication commonly used for smoking cessation, and among its side effects, nausea is noted to be the most prevalent. This gastrointestinal symptom frequently occurs due to the way varenicline interacts with nicotinic receptors in the brain and gastrointestinal system. Many patients report experiencing nausea, especially when they first start taking the medication or if they take it on an empty stomach. This side effect is significant enough that it can lead some individuals to discontinue the medication or adhere to it less strictly.

While insomnia, headache, and weight gain can also occur as side effects, they are typically less common compared to nausea. Recognizing the prevalence of nausea in patients using varenicline is important for clinicians, as it allows them to provide appropriate advice and management strategies to improve adherence and overall outcome in smoking cessation efforts.