(AP) — 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.

Reasons the drugs are so commonly prescribed include patients’ demands and doctors’ time pressures.

The studies were based on national health surveys from the late 1990s to 2010. The research is being presented Thursday at a medical meeting in San Francisco.