Adrenaline pills are items scattered around Liberty City in Grand Theft Auto III and Liberty City Stories as well as Vice City in Grand Theft Auto: Vice City that boosts the player's strength and slow down the game's time.
When collected by the player, the adrenaline pills give the player a temporary boost of speed while seemingly slowing down time. While the game's speed is slowed down, the player's aiming speed is the same as it would normally be, which is handy when engaged in gun battles such as police,gangs or during rampages. The player can also jump further than normal. Strangely, entering a vehicle resets the speed to normal again.
Many players consider the adrenaline pills to be a drug the player takes, which may also explain their absence in Grand Theft Auto: San Andreas and Grand Theft Auto: Vice City Stories, since the main characters in these games have a dislike towards drugs. However, in GTA San Andreas, an "adrenaline effect" cheat code exists which makes the same impact when entered
The official San Andreas strategy guide includes the locations of the pill all over the state so it could have been taken out during development.