What Causes Severe Weakness And Diarrhea Post Intake Of Sulfamethoxazole ?

My wife (78 years old) recently fell and shattered her elbow. Six days later she had a very long surgery and stayed in the hospital overnight. By the third day home, we felt she must have contracted urinary tract infection there, and when urine samples were taken, it was true. Our family doctor put her onSulfameth/TMP 800/160 mg, twice a day for ten days. During that time she experienced extreme weakness, some diarrhea, complete loss of appetite, and pain in her right leg as it decreased in size. She finished the treatment two weeks ago, but still has the extreme weakness, actually passed on in the bathroom during the night two nights ago, and can t tell whether she is constipated or blocked or has strange diarrhea (now small lighter-colored stool). We were finally able to get an appointment with the doctor for tomorrow morning. Do you have any opinion on this matter (we had assumed much of the weakness was due to the infection itself, but now wonder if it is all adverse side-effects of the drug?) Do you know of any drugs for e-coli that do not have such severe and lasting side-effects. The sheet the pharmacy gave us indicated that some of these symptoms might occur even months after she has been off the drug. Thanks. Well, now that I see you charge for your services, and we know nothing about you, forget it!!!!!