Syringe Spear and Poison

[Arcath d'Cardin]

What happens if I load a syringe spear with poison and coat it in a different poison? More of the same poison?

I'm asking because I'm trying to do a poisoner build, since the GM is running with the Unchained Poisons rule so it might actually not be a waste of space for a change.

[Entryhazard]

More of the same poison wouldn't be different of coating a weapon of multiple doses. It usually increase the DC or the duration but I don't remember the details.

[Nefreet]

Useful blog on poisons.