Caffeine, also known as methyltheobromine, is a central nervous system stimulant that humans consume daily. Found in coffee, tea, and other caffeinated beverages, caffeine has many side effects. Although caffeine can make the consumer more alert, there are health problems such as addiction and hypertension. Caffeine has a specific chemical structure that allows it to be easily absorbed in the stomach and intestines. It is derived from purines and is hydrophobic, which allows easy passage through cell membranes. (MOST POPULAR) For this reason the oral administration route is faster than the intramuscular route (PUB CHEM). After caffeine passes through the stomach, it travels to the liver where it is metabolized. The liver breaks down caffeine into theobromine, theophylline and paraxanthine, known as metabolites. (MOST POPULAR) After ingestion, elevated levels of paraxanthine are found in the blood. When blood flows through the liver again, paraxanthine is broken down into 1-methylxanthine. (MOST POPULAR) This process is critical to the excretion of caffeine. Due to caffeine's permeability, it can easily pass from one side of the cell membrane to the other. This property makes it very difficult for the kidneys to excrete caffeine. By converting paraxanthine to 1-methylxanthine, 1-methylxanthine cannot pass from the kidney membrane back into the bloodstream. Without this process, caffeine would remain in the body for days on end. (MOST POPULAR) As mentioned above, caffeine is a central nervous system stimulant. Caffeine stimulates the central nervous system by acting against another molecule, adenosine. Adenosine is a type of purine attached to a ribose sugar molecule. Adenosine is a part of… half of the article… the researchers concluded that the rats' typical slow waves were diminished by days thirty-one to forty-two. (DAILY) This meant that the rats slept less deeply and their sleep was less efficient in developing synapses. (DAILY) The researchers also noted that the lack of deep sleep impacted the rat's behavioral development. (DAILY) Typically, as rats get older, they become more curious. The population of rats in the experiment actually became more uncertain after consuming the coffee. (DAILY) While the results of this experiment do not necessarily suggest that caffeine intake for adolescents is dangerous, they raise a question for further investigation. Previously mentioned, caffeine has been considered a substance that can be abused and users can become addicted to it. Dr. Naoshi Ogawa conducted two case studies examining clinical caffeine dependence.