How do you dispose of unused medications?

What do you do with unused over-the-counter or prescription drugs? Drugs and pharmaceutical products include powerful chemicals that have saved or improved countless lives. But even small amounts of drugs need to be disposed of carefully so they don't pollute the environment or harm human health and wildlife. In early 2007 the government set guidelines for proper disposal of prescription drugs: http://www.whitehousedrugpolicy.gov/drugfact/factsht/proper_disposal.html