Caffeine: a new look at an age-old drug

Caffeine is ubiquitous in our environment and is the most widely used psychoactive drug in the world. Caffeine works on every system in the body mediated by the central nervous system. Caffeine has the opposite effect of adenosine and is the antagonist at the inhibitory A1-receptor. Caffeine elevates the free fatty acid mobilization and could enhance weight loss through pre-exercise caffeine ingestion. However, this hypothesis remains to be proven until an increase in fat oxidation is found. Caffeine is metabolized to more than 25 metabolites in man. Less than 5% of the caffeine is found in the urine as unchanged drug. The half-life of caffeine ranges from 1.5 to 9.5 hours. Smoking decreases the half-life of caffeine. Caffeine is used for the treatment of apnea of prematurity and as an additive in several analgesics and migraine remedies, and as a panacea for hyperkinetic children. Although much work has been done to establish the relationship between caffeine and cancer and mutagenicity, none of these have established a cause-effect relationship. The consumption of caffeine products in moderation appears to be safe at this point.