Nicotine, commonly known as nicotine, is an alkaloid present in Solanaceae plants (Solanum), an important component of tobacco, and a representative of N choline receptor agonists. The central nervous system has a role, no clinical value. Nicotine can be addictive or dependent (one of the most difficult drug addictions to break), people often have difficulty controlling themselves, and repeated nicotine use also increases heart rate and blood pressure and reduces appetite. Large doses of nicotine can cause vomiting and nausea, and in severe cases, death. Tobacco often contains nicotine, which prevents many smokers from quitting.