*SPOILER*
To get the endorphic blockers you need to go to the vault city doctor (first level of Vault 8) and talk to him.
This has been the only way I can get the jet antidote. Seems that you can give some jet to the same doctor and he'll come up with the cure, but I haven't been able to talk with him about it. I don't get that option. I had 90% doctor, 85% science, Int 10, Cha 10 and jet in my inventory. Any comment about it?