Despite my unfortunate fate (Which still would love to get explained ).
Willard Networks medical system knows 3 values for healing:
Bandage
Desinfectant
Painkillers
Bandages are actual HP. If you apply an item that gives 20 bandage value, you will over time get 20 real HP back.
Desinfectant increases the rate at which you gain bandage HP. Hence why a desinfected bandage heals you faster than a regular bandage.
Painkillers are "Fake HP". They go up very quickly compared to even bandages with desinfectant, but they are temporary.
Now, there is a "hidden" overdose mechanic behind painkillers. Every point of painkiller HP gained, adds to a value named "fake health". You can have 30 HP, but if that is caused due to taking damage after healing, your "fake HP" could be at 80. Fake HP essentially is just tracking howmuch painkiller HP you gained. Note that getting 80 painkillers from morphine at 70HP, would only add 30 to the actual fake HP value. As that is the actual HP you get from the painkillers.
Now, there is also a check for an overdose. I'm not sure what the exact math is exactly. But iirc it is something that compares your current actual HP, alongside your totalHP to the amount of fakeHP you have gained.
Essentially, if you heal too much of your HP from painkillers, you will die if your HP drops too low, or you simply gained TOO MANY painkillers.
The system automatically slays you if you have too much. This is why I personally have a slight aversian to health kits, first aid kits, biogel stuff. Because those all come loaded with painkillers ontop. They're great for quickly getting people up. But if fights/expos are long, they will start stacking up. And so if your group only has healing items with painkillers, eventually you will die.
This is why I like desinfected bandages. Decently fast healing, but no painkillers to OD on.
Might be a bit harsh to call it a noob trap, but essentially it is a noob trap. Technically speaking you can covertly kill someone in an expos by just rushing over to them and slamming them with morphine every time they go down. After 3 down or so they could've accumulated enough fakeHP to OD and die.
Anyways I hope that explains it.