All the fluoroquinolones can cause tendon problems...these meds include Cipro and Levaquin (the most common ones) as well as Avelox (sometimes used for respiratory infections) and a couple of others that have been taken off the market for various reasons. I wonder if that's why the OP's doctor recommended taking it easy for a few days as opposed to the UTI itself...as far as the UTI I think it would depend on how bad the infection is and how one is feeling--listening to your body is a pretty good guide any time you're sick.