Repeated warnings that antibiotics don't work for most sore throats and bronchitis have failed to stop overuse. Two studies show doctors prescribed these drugs for most adults seeking treatment at a rate that remained high over more than a decade. Antibiotics can have bad side effects, including severe diarrhea. Inappropriate prescriptions put patients at needless risk and can cause drug-resistant germs. Antibiotics only treat bacteria but most sore throats and bronchitis are caused by viruses.