Houston Mayor Annise Parker says people often don't know what to do with unused prescriptions.
"It is a problem in cities all across the country that when people decide that they're going to flush unused medications -- we really need to get the word out that is inappropriate. It has caused, in some places, significant problems with these drugs entering into the water supply. We would encourage people to bag them and bring them to one of these periodic drug drop-off locations."
A number of sites will participate this weekend in the drug enforcement agency's national drug drop-off.
You can find a list of locations at National Take Back Initiative Collection Site Search.