Jim, I can tell you that when I got a lot of UTIs as a kid, I was treated with an anti-biotic called Macrodantin, and one called Macrobid. Those are more specifically made for UTIs. But I don't see why doxycycline wouldn't work.

You might also want to post your questions on the Men's Health board, Urology board, sexual health board or men's sexual health board. People there might know more about how to treat UTI, etc...