Those just-in-case pills health officials hand out to people living near nuclear power plants are in big demand, even in Southeast Pennsylvania--more than 6,000 miles away from the radiation leaks in Japan.

Some people think of the potassium iodide as a cure-all, anti-radiation medicine. But Dr. Susan Mandel, the director of the Penn Thyroid Center, said the salt pills have a very specific use.

"It literally feeds the thyroid, so it prevents the thyroid from taking up the damaging radioactive iodine. It doesn't protect against any of the other radioactivity that's being released, and it doesn't protect any other organ,” Mandel said. “It doesn't protect against plutonium, cesium, all those other things.”

The Pennsylvania Department of Health typically gets five or six calls a week from people wondering how to get the potassium iodide pills, also known as KI pills. Last week, the agency logged more than 300 calls.

A doctor with the agency said KI pills should be taken only on the advice of a doctor--or emergency management and public health officials.

Dr. Fred Mettler, a radiologist with the University of New Mexico, led the U.N. team that reviewed the health effects of the Chernobyl disaster.

He said there are some health risks associated with taking the pills, and they should not be used as preventive medicine.

KI pills have a very short treatment window, and are supposed to be used just after a radiation contamination. The protection wears off after about 24 hours. The salt pills are primarily recommended for children, pregnant women and young adults. Adults over 40 have the lowest chance of developing thyroid cancer after a radiation exposure.

The Centers for Disease Control and Prevention sent out tweets last week to clear up confusion.