I'll try to go without plugin first.
For the items you could always use a common event inside the item, and put in the item damage formula this :
v[x] = b.actorId(); 0;
replace X by the ID of your own variable, it'll store the actorID inside this variable. Now in the common event triggered by your item, check the player's health like this (place a condition, then use a script for the condition) :
$gameActors.actor($gameVariables.value(x))._hp <= y
where again x is the ID of your own variable where you stored the ID of the actor previously. y should be the number of HP your pill actually remove from the player, if you want you can make it a variable too, like this :
$gameActors.actor($gameVariables.value(x))._hp <= $gameVariables.value(y)
where Y is the ID of your own variable where the damage dealt by the item is stored. this condition script will be fulfilled if the hp of the actor is lower than the damage it would takes from the item (so, if the actor reaches 0 hp by consuming it), enter there the code to be executed, then call the game over scene.
and if the condition is not met, simply remove from the actor's hp the value, with this script call :
$gameActors.actor($gameVariables.value(x))._hp -= $gameVariables.value(y)
and done !

lemme know if I got something wrong if you have any issue with it.
EDIT : corrected the code !