When injected, a super stimpak heals 75 HP immediately, but the powerful nature of drugs used in the process will cause an adverse reaction from the organism, resulting in draining 9 HP after two minutes.
The super stimpak is a rare sight in the wasteland, usually only available from high tech settlements, such as Vault City or San Francisco.
Super stimpaks also have a nefarious purpose. They can be used to assassinate friendly non-player characters in populated areas; no one would suspect killing a person with stimpaks, because they heal people. Having the Awareness perk helps, as one can see how much health the target has. Simply divide their maximum health by 9 and round up. The number reached is how many super stimpaks needed to kill the victim. Stick the stimpaks in a weapon slot (for convenience and speed) and use the applicable number of stimpaks on the victim. After waiting 2 minutes, they should die from the latent damage (9 points per pak').
Five are found inside of an ice chest located in the room where Dr. Wu is located in The Cathedral's interior. This ice chest is locked, however, and must be lock picked in order to open it. In the higher levels of The Cathedral, Morpheus possesses one super stimpak.