My Father-in-law Is 94 Years Old And Went To Urgent

My father-in-law is 94 years old and went to Urgent Care on Monday for frequent urination. He had no bacteria in his urine but was put on Bactrim empirically. He did have sugar in his urine and he is diabetic. The culture came back negative and he has finished his 5th day of Bactrim. Today he is very weak and vomited twice, vital signs are stable. Should I take him off the Bactrim?