If you look for pharmaceuticals and hormones, you can find hundreds of them coming out of any sewage treatment plant; it is a nation-wide problem. Contamination not only results from flushing pills down the toilet, but also from unmetabolized drugs that we release in our urine and feces. This means that getting people to dispose of unused drugs appropriately, while a terrific idea, will not solve the problem. With the volume of waste running through our sewage treatment plants, there is currently no feasible way of preventing environmental contamination by pharmaceuticals.
One of the most effective things we can do to lessen the pharmaceuticals we are pumping into aquatic ecosystems is to choose to not use unnecessary pharmaceutically-active compounds, such as the antimicrobial compound triclosan. Triclosan is the active ingredient in most over-the-counter products that say "antimicrobial" on them, including hand soap, toothpaste, and socks. It is totally unnecessary. Regular soap kills germs too; there is no reason you need to buy "antimicrobial hand soap" unless you are performing surgery.