WHAT TO DO WITH THOSE UNUSED OR OUTDATED MEDICATIONS IN YOUR HOME?
This is a topic that I beleive most people aren't aware of. When I ask people if they know what they're supposed to do to properly dispose of this type of waste, the answer is usually "throw them down the toliet or sink". WRONG ANSWER!
As with any waste, the method you choose to dispose of unused medications has a profound effect on the environment. Unused medicines that are disposed of via the toliet/sink method end up where? In the groundwater. Water treatment facilities are not equipped to deal with everything, and medicines are one of them. Consider them as HAZARDOUS WASTE. Some pharmacies will take unused medications (they don't hhave too, but 'some' will do this and return them to the manufacturer for proper disposal).
For those of you with your own water waste receptible such as a septic system, if you pour your medicines in toliet/sink, it will end up directly in the water table, eventually coming out somewhere, either in the nearest lake or stream, or even out in your field, where wildlife will become at risk.
I've done alot of reading on this subject and the conseses is either to ask your pharmascist if they will take it from you, or call your local household hazardous waste facility. It is even better to throw them in the trash, than to use the flush method of disposal.
I've just searched Google and there seems to be a wide variety of answers to this question, some of them by state. When in doubt, make a call to your local Household Hazardous Waste Facility or your pharmacy and get some direction from them.
BEFORE I CONTINUE FURTHER, THERE IS ONE MORE IMPORTANT THING TO BE AWARE OF:
DO NOT UNDER ANY CIRCUMSTANCES DISPOSE OF HYPODERMIC NEEDLES IN THE TRASH....
These items ARE HAZARDOUS WASTE!
Let me tell you it was no fun the day I discovered several coffe cans full of used syringes that had been thrown in one of our dumpsters last summer when I was working at a recycling/solid waste disposal facility. Of course, upon being thrown in the dumpster, they opened up and had spilled all over inside that dumpster and landed everywhere. Guess who had to go dig them out? It was very scarey business let me tell you, and the first thing I did with them was to take them to the Househole Hazardous Waste facility where they were supposed to be dropped off in the first place. Most diabetics and others that use the syringes are supposed to be aware of this, however some people (alot, it is frightening!) do not want to take the time to properly dispose of their waste. Also, if the person that had used those syringes are now passed on leaving the family/friends to do the "cleaning out", so to speak, may not be aware of the fact that these are NOT just regular garbage. OK, so now you all know what to do with those things, PLEASE do the right thing with them, they are very dangerous!
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Here are some of the answers I've found about medication disposal. Tthe following article 
contained most of the information in one site I thought would be helpful...
Traces of pharmaceuticals in U.S. waterways may have harmful effects on aquatic life.
Scientists across the country and across the world have found pharmaceuticals like estrogen, cholesterol-lowering drugs, pain relievers, antibiotics, caffeine and even anti-depressants like Prozac in waterways like lakes, rivers and streams. Medications can harm aquatic life, dangerously alter the chemistry of natural water, and could possibly find their way into our drinking water. Despite the recent findings, there is no national coordinated testing system that requires municipalities to test their waterways for pharmaceuticals.
Just south of Las Vegas, the Southern Nevada Water Authority is testing the water in Lake Mead for pharmaceutical contamination. Project Manager Shane Snyder says that over the last several years of testing, they found small amounts of 20 different pharmaceutical products in the lake. The concentrations of the pharmaceuticals they are finding are about seven or eight times smaller than therapeutic doses.
Researchers think that the pharmaceuticals are getting into waterways through wastewater. In many cities, treated wastewater flows into open bodies of water as part of water recycling programs. The wastewater is treated, but not for pharmaceutical contamination. Current water treatment facilities filter out bacteria and other contamination, but they were not designed for, nor have they been retrofitted to test for and eliminate pharmaceutical contamination before the wastewater is released into the environment.
Scientists believe that the drugs are getting into the wastewater in two different ways. First, people often flush unused and/or expired medications down the toilet. Second, Janet Raloff reports in Science News, March 21, 1998, up to 90 percent of a drug taken orally can be excreted. Scientists don't know which source of pharmaceuticals is a larger problem, so the issue of pharmaceutical contamination is both a water treatment problem and a responsible disposal problem.
Drugs found in the waterways can cause at least two potential problems. First, many scientists say drugs can have significant detrimental impacts on aquatic health like growth and reproductive problems for fish, or toxic effects on plant life. Second, some scientists like EPA chemist, Christian Daughton say these chemicals can also have a potential human health risk if the contaminated water gets into drinking water supplies.
Daughton also says we should be thinking about systematic, nationwide testing for pharmaceuticals in waterways and water supplies -- perhaps as a collaboration between the EPA and the USGS. But, he says such testing is confounded by the fact that scientists still don't know exactly what drugs they should be most concerned about. Until research scientists have a better understanding of which pharmaceuticals are in the water and causing the most damage, water treatment facilities would have a very hard time developing an effective method for filtering them out.