A death in the family left me with some prescription drugs.  I thought that I shouldn't just toss them or flush them, but wasn't sure what to do with them.  Turns out, a lot of sources begin by saying "don't just throw them a way or flush them down the toilet," then end by saying to throw them away or flush them down the toilet.

Experts say the safest way to get rid of unwanted drugs is through a community "take back drugs" day, a collection center, or to deliver them to a pharmacy that accepts them.  Unfortunately, the timing or the time it takes can make those options difficult.

Near as I can tell, the most convenient and proper, if not best, way to dispose of old prescription drugs is to:

• 
  If they're on the FDA "Flush List," flush them down the toilet.
  
• If they're not on the Flush List, put them into a container, like a bag or a can.
• Add water to dissolve them.
• Add something like cat litter or coffee grounds to disguise them from people who might find and want to ingest them.
• The put the container in the trash.

To preserve your privacy, it's a good idea to remove labels (frustrating) or cover up identifying
information on bottles before throwing them away.

Oddly, these these recommendations aren't intended to protect the environment.  The flush list is to get rid of especially dangerous drugs in a way that keeps people from finding and using them.  The coffee grounds or cat litter are to disguise the drugs, not to "deactivate" them.

According to the FDA, it's not the flushing of unused drugs that's causing problems for fish; the fish are getting drugged by medication that people take, then excrete into the sewage system.  For instance, an anti-diabetes drug can cause male fish to become somewhat female.  Anti-depression drugs in human waste causes some male fish to lose interest in female fish.   Contraceptives can cause some fish to stop eluding predators.  Natural predators.  There's no evidence that salting rivers with contraceptives will up your fishing game.

While we're on the subject, the problem goes the other way too.  People shouldn't take antibiotics intended for fish.  Fish take antibiotics?  People take fish antibiotics?