Tri-ox is a simple but effective intravenous medicine used for quickly enriching a body of oxygen, especially in an oxygen-poor environment such as Vulcan. Most humans and humanoids would have trouble breathing on Vulcan, especially during any strenuous work or other exertions. The use of tri-ox helps alleviate this. The drug also substitutes for cumbersome breathing masks and equipment.
Doctor Leonard McCoy faked using tri-ox on Captain James T. Kirk in 2367 during a Vulcan combat ritual (TOS: "Amok Time"), and used the drug on the captain after his space suit's air supply had nearly run out.(TOS: "The Tholian Web"). Tuvok used tri-ox on survivors of an orbital teather carriage in 2373. (VGR: "Rise")