Now, I don't know so will pose the question as to antibiotics and generic meds durability. Not sure that antibiotics will remain stable much past the expiration date. And, generics are not that stable either.
Disposal of old/unwanted meds is probably best burnt in an incinerator. Land fill does not want them and they tell us not to flush them as it really pollutes the drinking water. May be a competition to the local bars.
My wife has been on some expensive meds for 20 years due to Lupus, epilepsy and MS. Some stuff works and then when it wears out its welcome, you have this partial fill left. Burning is the only vialble option that I can come up with. We used to put her spent injections in a plastic milk jug and tape the lid shut. It went into the land fill that way. Hmmmm! What to do?