Caffeine is the most commonly abused drug in the entire world. It is a quick-acting natural stimulant that that stays in the body for about 3-7 hours. It can cause blood pressure to raise and heart rate to increase. The most common source of caffeine is the coffee bean—a natural source—and in a cup of coffee less than 2% of what is being consumed is actually caffeine, the rest of the compound is made up of lipids, carbohydrates, and fats.