Emergency and space medipen

I DON’T UNDERSTAND!!! How do they work? In Runet they say that the space medipen does not allow pressure to kill and gives immunity for a while from oxygen starvation, but it does not do this!!! And extra medipen does not allow a person to get into a critical condition, but it too does not do this!!! 
please answer me and explain what they are doing?/
Thanks you for much

Space medpens contains barozine, which can prevent low pressure damages (aka spacings), it probably have leporazine since it also adjust body temps higher/lower if the user is in a low/high temp area (Space)

Space medpens can OD if you inject to much, one pen is enough for short period time of no EVA suits, but space medpen does not protect you from high pressure (plasma fire)

Emergency medpen (or E-medpens) have epinephrine (heals when damage passes 100/crit ) and tranex acid (stops bleeding), which is useful for reviving people who got into crit if they did not take too much damage post crit.

However, emergency medpen can OD very easily, one pen is enough for about half a minute, you can use it if you have heavy bleeding or near crit (since tranex acid), you can also use it on others to stable them before dragging them to medbay

Space pen = Anti space pressure pen that keeps you alive from no space suits
Emergency medpen = The magic medpen that stables people in crit and stops bleeding (useful for fighting rats)

Checkout the chemistry page for more info on OD threshold: https://wiki.spacestation14.io/wiki/Chemistry#Medicine

Okay, im understand. apparently all these substances are few in them, so they do not always work) 
Thanks you

both medipens have nearly the maximum amount you should ever put in someone actually, you just have to act fast