This question about two-part poisons got me to thinking if the poison described by Mollari could even be effective as form of persuasion. Mostly because the second part could be administered weeks or even years after the first part.
In the episode, Ceremonies of Light and Dark, Londo Mollari used a two-part poison to persuade Antono Refa to change his policies.
Refa: You walked away from the greatest power I have ever seen! And now you expect me to do the same? They are the key to my eventual rise to the throne! Why would I abandon them?
Londo: Because I have asked you. Because your loyalty to our people should be greater than your ambition. And because I have poisoned your drink.
[Lord Refa looks in astonishment at Londo.]
Londo: Yes…and it is very interesting poison. It comes in two parts. Both are harmless on their own. But when combined…quite lethal. The first settles into the bloodstream, and the intestinal walls. It stays there for years. Silent…dormant…waiting. When the other half of the poison enters your system the two meet, have a little party in your cardiovascular system … and suddenly, you are quite dead.
Refa: Why? Why did you do this?
Londo: To guarantee your cooperation! And because sooner or later, you would do it to me! As we are returning to the old ways, Refa, and poison was always the instrument of choice in the old Republic, being something of a sentimentalist, I got here first.
Refa: What do you want me to do?
Londo: You have encouraged that fool Cartagia to attack worlds that have no value to us. You will now encourage him otherwise. You will bolster our lines of defense around Centauri Prime. And you will have nothing more to do with Mr. Morden. If you do not comply, one of my agents in the royal palace will introduce you to the second half of the poison.
[Mollari raises his glass and grins.]
Londo: To your health, Lord Refa.
Surely the palace doctors back on Centauri Prime would know about all kinds of poisons since poison was the weapon of choice against political opponents in Centauri culture.
A high ranking official like Lord Refa would ask his doctor to check for any poisons. Londo described the behaviors of the poison, so Refa could pass that knowledge to the doctor. That might help the doctor identify the exact poison.
Why would Londo Mollari even assume a two-part poison would work? He would know that poison victims would just ask for medical help. (Unless the poison could not be removed, or unless he was just bluffing.)
I'm looking for an answer from the tv shows, movies, or novelizations that mentions anything related to this poison. I don't want answers from fanfic.