Adrenaline was a substance that naturally occurred in the body of humans and the Zillo Beast.
Shortly after the formation of the Galactic Empire, an Aurebesh data readout accessed by Clone Force 99 member Tech aboard the Marauder noted that the creature had a "HIGH ADRENALINE" level.
During the Galactic Civil War, Imperial officer Firmus Piett felt a surge of adrenaline when he entered Darth Vader's meditation chamber aboard the Executor and realized just what Lord Vader could do, and just what it meant to him. After The Contessa assigned Wedge Antilles to cobble together a makeshift squadron to neutralize a new pirate threat, the two got into a discussion about the role of adrenaline in combat. When attacking an Imperial stormtrooper, Isabalia was propelled by fear and adrenaline as she punched him with all she had. When Willrow Hood attacked a stormtrooper on Cloud City, he whipped a camtono into their rifle as desperation mixed with his adrenaline. When stormtrooper Deena Lorn defected from the Empire, she thought to herself that "Maybe it was the adrenaline, the fatigue, maybe it was the years of anger and hatred" and also reflected on how she had previously left the carbon-freezing chamber in Cloud City in an adrenaline-fueled daze.
- Rise of the Separatists