Hundreds of pounds of unwanted medications were turned in to Washington area police departments Saturday, as residents emptied their medicine cabinets for a nationwide drug take-back day.

Howard County police said they collected 862 pounds of unwanted, unused and expired medications, both the prescription and over-the-counter varieties, as part of the federal Drug Enforcement Administration’s National Take Back Initiative.

The DEA said removal of unwanted prescription drugs helps prevent “experimentation, addiction, overdose and even death.” Officials also have cited the need for keeping discarded drugs from endangering water supplies.

In Alexandria, the police and sheriff’s office collected 243 pounds of what were described as potentially dangerous prescription drugs and other medications.

In Anne Arundel County, police said they received several hundred bottles of medications — expired, unused or both. The items, which weighed about 350 pounds, were placed in plastic trash bags for disposal, police said.

The total from the three jurisdictions amounted to nearly three quarters of a ton. Results from other areas were not immediately available.

The take-back day was the seventh held around the country by the DEA and local jurisdictions. The DEA said that amounts collected at the first five events totaled more than 1,000 tons.

That figure does not appear to represent the full measure of Americans’ unwanted pills. At least two local jurisdictions have issued detailed instructions for safe home disposal of medications.

In Arlington, where trash is incinerated, residents were advised to remove pills from containers, dissolve them in water and place them in some “unattractive substance” such as used coffee grounds or kitty litter. The next step is to throw the concoction into the garbage.

Montgomery County residents were reminded to take labels off pill bottles and place the empty containers into their blue recycling bins.