Health stims were injectable healing medications. A few of them were located inside of medpacs.
Darth Bane made use of a health stim that he retrieved from within a medpac. After crash-landing the cruiser Valcyn on Dxun, he was in dire need of immediate medical attention due to severe injuries. Discovering a medpac kit in the cockpit, he found several undamaged health stims. He injected one into his thigh, and almost instantly, the health stim amplified his body's innate healing abilities. Furthermore, the health stim had a pain-reducing effect.