If it was the pill he took on the train (with Buscetta) after the Tahoe shooting, I bet it was Miltown, the universal tranquilizer of the late Fifties and into the Sixties (the Stones sang about it in "Mother's Little Helper").
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.