Yeah, I don't know how I feel about the whole 'ghouls need specific drugs to keep from going feral' thing that the show adds to the lore. It could've been something specific to Cooper's character (since it also clearly affects his breathing), but the ghoul he killed and ate was asking for a hit of it as well when he was showing signs of madness. Plus the drug is clearly a known and valued commodity if the organ harvesters kept such a large stock of it.
It might be a new contrivance on Bethesda's part to help cope with the fact that the further these games get from the day the bombs dropped, the less plausible it is that there are still pre-war ghouls who haven't yet gone feral (since the game lore occasionally hints at the fact that they need a particularly strong willpower and / or a goal to focus on to keep that from happening).
Simple questions deserve long-winded answers that no one will bother to read.