guarana
n. a shrub (Paullinia cupana) indigenous to the Brazilian Amazon, the seeds of which were originally thought to contain guaranine, a methylxanthine compound that is essentially indistinguishable from caffeine. It is now known that guarana in fact contains a significant amount of caffeine, which is its primary active ingredient, as well as lesser amounts of the methylxanthines theophylline (the active ingredient in tea) and theobromine. Used as a stimulant and appetite suppressant, guarana is available in many over-the-counter preparations in the United States and other Western nations. At recommended doses, it appears to have the same mild adverse effects known to be associated with other sympathomimetic stimulants (e.g., restlessness, increased urination, gastrointestinal distress) but may interact with medications, particularly monoamine oxidase inhibitors. Additionally, additive effects and potential toxicity may
occur when guarana is combined with other caffeine-containing products, and there is growing concern that use of guarana-containing products may cause such serious adverse events as chest pain, irregular heartbeat, seizures, coma, and possibly death.