Caffeine
Caffeine (C8H10N4O2) was a stimulant that was present in a variety of foods and beverages, including coffee and raktajino. Beverages with the caffeine removed were known to be decaffeinated.

It could be somewhat addictive to most humanoids if consumed on a regular basis (excluding Vulcans, according to T'Pol). () 

According to , a Zariphean blend had enough caffeine in it to keep a Human awake for three days straight. ()

In 2153, when  suffered heavy damage to its armory, Lieutenant Malcolm Reed drank black coffee instead of consuming his usual tea and crumpets, stating that he could use all the caffeine he could get. ()

In 2370, a spectroscopic analysis of the liquid in Miles O'Brien's cup found vegetable-based oils and caffeine, leading Keiko O'Brien to conclude that it was in fact coffee he was drinking in a video clip. ()

In 2375, after seeing Kathryn Janeway drink a large amount of coffee, Neelix suggested that he ask The Doctor to prepare a hypospray instead so she could absorb the caffeine more directly. Janeway took the hint and decided to stop after her current cupful. ()

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Drugs