Mako root

From Memory Alpha, the free Star Trek reference.

The mako root is a plant native to the planet Neural. It is the only known cure for the poisonous bite of the deadly Mugato, and then only when properly administered by a female shaman of Neural's Hill People known as a Kahn-ut-tu.

The treatment is highly ritualized.

The ritual involves the beating of drums and chanting of certain incantations as the shaman creates a wound in his or her own hand, takes hold of the mako root against the wound, then presses it against the victim's wound. The root then seems to move of its own power as it draws the toxin out. It may act as a filter between the two circulatory systems to help screen out the poison. It is unknown if the ritual itself has anything to do with the healing processes, but the root certainly has an effect of cleansing the body.

Incidentally, the ritual also acts as a pseudo-marriage ceremony between the victim and the administering Kahn-ut-tu shaman, as the victim now owes the shaman his or her life. (TOS: "A Private Little War")