ERA on page 547
@Panda, Rothwell mentioned the docs telling him that the drug wouldn't kill Charlie, as I recall. That's not mystery drug from the future, it's probably a narcotic, barbiturate, or other sedating drug which can be found in a hospital. Given the implication of difficulty handling the OD, I imagine it might have been a barbiturate, but given the assumption it wouldn't kill Charlie it could have been something like a benzodiazipine, maaaybe a narcotic they thought he'd only give a low dose of... plenty of options, none of which would be a mystery to ER personnel.