A medical kit is a tool which only exists in SLASH'EM. It appears as a leather bag when unidentified, but cannot hold anything except pills, bandages and phials. To view the contents of a medical kit, drop it and #loot it. There is no way to refill an empty medical kit.
Only Healers can use the bandages (to bandage their wounds as part of their surgery technique). Only members of the Vampire race can use the phials (to draw off a phial of their own blood for later consumption).
Anyone can apply a medical kit to swallow a pill from it, but only Healers can reliably do this successfully, and then only if the kit is not cursed. If the pill works, it will cure your first trouble from the following list: sickness, blindness not caused by a thrown cream pie, hallucination, vomiting, confusion, stunning, and lack of hit points (it will heal you by 10-19 HP but won't increase your max HP). If the pill fails, it may have no effect, cause HP loss, or make you deathly sick.
Chances of success:
|Status||Healer||Monk, Priest, Samurai, or Undead Slayer||Other Class|
This spoiler on tools in SLASH'EM has more detail on medical kits.