My Father 83 Is On Bactrim To Clear His UTI

My father 83 is on Bactrim to clear his UTI which is causing him to have hallucinations at night, although his doctor is saying the Bactrim is not causing him to hallucinate. I disagree... based on what I am reading with other patients and studies. Is there another drug that is just as effective, or should he just push through this as most studies .