Levaquin
"My mother is 84 and was given this drug for a mild UTI.  After 2 doses, she became so confused she didn't know where she was or who I was.  Her muscles were so weak she could not move or stand.  She was paranoid and manic at times.  Her potassium dropped very low.  She was in the hospital 4 days.  They immediately took her of it, gave her IV's and potassium.  Tested her for stroke and dementia, which were negative.  She is home and better but it took several weeks.  Not a good drug, especially for elderly.  She now takes D-Mannose 1000mg/day, 2000mg for any UTI symptoms."