If you have unused medications (prescription or non-prescription) you no longer need or want, you should not dispose of them by flushing them down the toilet.
Twice each year the Drug Enforcement Administration (DEA) sponsors a National Drug Take Back Day to assist in the safe disposal of these medications.
Additional information regarding the proper disposal of unwanted medications can be found on the web sites of the Food and Drug Administration (FDA) as well as the Environmental Protection Agency (EPA).