**Core Concept**
Nicotine de-addiction involves the use of medications to manage withdrawal symptoms and cravings associated with quitting smoking. Various pharmacological agents are employed to help individuals overcome nicotine dependence.

**Why the Correct Answer is Right**
Varenicline (Chantix) and bupropion (Zyban) are well-established medications for nicotine de-addiction. Varenicline acts as a partial agonist at the α4β2 nicotinic acetylcholine receptor, thereby reducing the rewarding effects of smoking and alleviating withdrawal symptoms. Bupropion, on the other hand, is a norepinephrine-dopamine reuptake inhibitor that helps regulate mood and reduces cravings.

**Why Each Wrong Option is Incorrect**
**Option A:** Varenicline is indeed used in nicotine de-addiction, so this option is incorrect.
**Option B:** Bupropion, as mentioned earlier, is also used in nicotine de-addiction, making this option incorrect.
**Option C:** Nortriptyline, a tricyclic antidepressant, is not typically used for nicotine de-addiction. It may be used off-label for smoking cessation, but it is not a first-line treatment.

**Clinical Pearl / High-Yield Fact**
When considering medications for nicotine de-addiction, it's essential to remember that varenicline and bupropion are both FDA-approved options, whereas nortriptyline is not a standard treatment for smoking cessation.

**Correct Answer:** C. Nortriptyline