A nurse is providing teaching about varenicline to a client who is in a smoking cessation program. Which of the following statements should the nurse make?

Varenicline (Chantix) is a partial nicotinic acetylcholine receptor agonist used for smoking cessation. The standard prescribing instruction is to begin taking the medication one week before the planned quit date. This allows the drug to reach steady-state plasma concentrations and begin reducing the rewarding effects of smoking before cessation occurs, improving the likelihood of successful quitting. There is no clinically significant grapefruit interaction with varenicline; grapefruit warnings are most relevant for drugs metabolized by CYP3A4, and varenicline is primarily renally excreted unchanged, making that statement incorrect. While varenicline can cause vivid dreams, insomnia, and nausea, drowsiness is not a primary or commonly emphasized side effect to teach, and calling it a drowsiness-causing medication without context is misleading. Regarding the treatment course, the full standard course is 12 weeks, not 30 days, and a second 12-week course is often recommended for clients who successfully quit and wish to reduce long-term relapse risk — so saying the course is only 30 days and cannot be repeated is factually incorrect. Therefore, starting the medication one week before the quit date is the accurate and clinically appropriate teaching point.