example, just making up the dosages etc.
you get scripted 100mg. usually you have to snort the 100mg to get what you need. when going to injecting, perhaps you will only need to shoot 80mg to get the same effect. soon enough as tolerance builds, you will have to start shooting 90mg, then 95, then up to 100mg where you were to start with.
snorting 100mg obviously isnt enough anymore - to get the same effect as shooting 100mg, you'd have to rail maybe 120mg which you dont have.
if you think about the eventual ending to this story, i could anticipate that you'll start shooting your oxys as well etc.