Adrenaline was a naturally occurring substance within the bodies of both humans and the Zillo Beast.
Not long after the establishment of the Galactic Empire, Tech, a member of Clone Force 99, discovered an Aurebesh data reading while on the Marauder. This reading indicated that the Zillo Beast possessed a "HIGH ADRENALINE" level.
During the time of the Galactic Civil War, Firmus Piett, an Imperial officer, experienced a rush of adrenaline upon entering Darth Vader's meditation chamber on the Executor, as he comprehended the full extent of Lord Vader's power and its implications for himself. Following The Contessa's assignment of Wedge Antilles to form a makeshift squadron to counter a new pirate menace, they engaged in a conversation regarding the function of adrenaline during combat. Driven by fear and adrenaline, Isabalia struck an Imperial stormtrooper with maximum force. In a similar vein, Willrow Hood, fueled by desperation and adrenaline, attacked a stormtrooper on Cloud City by using a camtono to strike their rifle. When Deena Lorn, a stormtrooper, deserted the Empire, she pondered, "Maybe it was the adrenaline, the fatigue, maybe it was the years of anger and hatred," and also recalled exiting the carbon-freezing chamber on Cloud City in an adrenaline-induced haze.