Nicotine bitartrate dihydrate is a crystalline salt form of nicotine often used in pharmaceutical formulations and nicotine replacement therapy products. It is known for its rapid absorption and bioavailability, making it effective for delivering nicotine to the bloodstream.

On the other hand, nicotine polacrilex, also known as nicotine resin complex, is a resin-based form of nicotine used in nicotine gum and lozenges. It is designed to release nicotine slowly, providing a controlled delivery of nicotine to help alleviate cravings and withdrawal symptoms.