Pyridium is a dye that coats the lining of the bladder relieving pain and should be used in conjunction with antibiotics. It turns urine orange or red so I imagine it could do the same to breastmilk. The only cautions I found was that it is contraindicated in renal or hepatic insufficiency. My book says that the drug should be stopped in 3 days if pain is relieved. Briggs says no BF data is available. Another thing I learned when I was having cronic UTI's my doctor said to be sure to empty my bladder before and after having intercourse...it worked haven't had one since.