Usually pharmacies sell a thing to mail them off. Sometimes police stations will take them. If you need them out of your house rapidly you can mix them with kitty litter and water and put it in the trash. It dries into a hard rock. Not environmentally friendly but what hospice used to do where I worked and it worked for me when I had to get them out of the house immediately. Much easier than flushing pills that float right back up to the surface.