Welcome to NeuroTalk Sarabeth!
I'm sorry for the pain you're having from TN and that it's causing you to miss work. I can understand how hard it must be when you're still in the probationary period for a new job. They should have some sort of exception allowance especially with the H1N1 flu going around. If somebody showed up with that, even the job trainers could get sick then what would they do?
About the Topamax, were you getting to the point that you were underweight? I agree you are owed an explanation of why you can't have it. Did you explain to the doctor that you might lose your job if you can't deal with the pain? And that the Topamax is the only one that was helping?
Good luck with everything and keep us posted.