From an environmental standpoint the most important thing residents should know is what not to do. Specifically: Don't flush medicine down the toilet or down the drain. They could harm your septic system and the effluent from your system joins the groundwater. Some medicines can persist in and migrate through the ground for years. Traces of many medicines can already be found in ground and surface water. Don't add to the total.
Don't put medicines in the recycling bin. It could easily be released into the environment during recycling.
All household trash from Madison is not put in a landfill where medicines would eventually leach into the groundwater: It is incinerated, thus effectively destroying all such medicines. So the simplest disposal option is to put medicines in your household trash.
Before placing medicine in the trash:
Remove the identity of the medicine
Remove the identity of the person for whom it was prescribed
Denature medicine to keep it from being used again
Any liquid will denature pills
Salt, baking powder, kitty litter etc. will make liquids unusable
Conceal - wrap in opaque packaging and tape tightly
Sharps (needles and lancets): wrap in puncture proof container and tape closed
Unopened vials IV bags etc. - wrap in leak-proof packaging and tape closed