Well, I can offer a personal experience:
I was recently placed on Macrobid for a UTI and when I filled the scrip at Target, the big name they put on the bottle was for Nitrofurantoin. OK, I'm used to that. But my nursing education had me carefully checking the bottle until I found teeny tiny print that stated it as generic for Macrobid.
Then not quite 3 days later I developed very bad side effects. N/V, numbness/tingling in my lower extremities that I blamed on long hours on my feet (hence the prob cause of the UTI) and thought that this must be a drug reaction. I have very similar allergic reactions to sulfa drugs. So I pulled out the Davis Drug Guide (our Bible!) and couldn't find a relation to sulfa, or is there?
The literature tells me it's not an allergic reaction, but a few weeks later a urologist said that it was; he also told me that Macrobid is a very strong drug and even though I stopped on the 3rd day, on a 2 week regimen, he said that was probably long enough to make the UTI go away.
(funny acetomiophen and Tylenol. Watch out for the APAP! LOL