Caffeine Anhydrous is a bitter, white crystalline xanthine alkaloid that acts as a stimulant drug and a reversible acetylcholinesterase inhibitor. Caffeine is a chemical found in coffee, tea, cola, guarana, mate, and other products. Caffeine is most commonly used to improve mental alertness, but it has many other uses. Caffeine is used by mouth or rectally in combination with painkillers (such as aspirin and acetaminophen) and a chemical called ergotamine for treating migraine headaches. It is also used with painkillers for simple headaches and preventing and treating headaches after epidural anesthesia. Some people use caffeine for asthma, gallbladder disease, attention deficit-hyperactivity disorder (ADHD), shortness of breath in newborns, and low blood pressure. Caffeine is also used for weight loss and type 2 diabetes. Very high doses are used, often in combination with, as an alternative to illegal stimulants.