I used to get UTIs a lot. They're terrible and uncomfortable and then the antibiotics lead to lovely yeast infections since your balance gets thrown all off...
I finally jumped off the antibiotic train and got proactive about it...the most valuable thing I found was that peeing rids your body of like 98% of the bacteria in your bladder and urinary tract, so even though it's uncomfortable, it's important to pee a lot. Drink as much water and high-acid juice (real cranberry, not the sugary stuff, and grapefruit juice are great) as you can stand, pee all the time, and your body can heal it up naturally. I can't speak to that particular drug, and I would never go out on a limb and say to ignore your doc's advice, but if you can give yourself a little time and see how you do, maybe you can avoid the whole antibiotic thing altogether?
Preventative--pee after sex, every time. Bacteria is pushed into the urinary tract during sex, peeing gets it out.
Best of luck...