There are drugs such as tetracyclines that should never be used past their expiration dates because they degrade into toxic compounds. Certain classes of drugs such as anti-arrhythmics or drugs like warfarin are dosing critical to the point where I would not want them if they were out of date.
I worked in pharmaceuticals in a medically underserved community for a couple of years. At that time when drug samples expired, sales representatives had to return them to their companies for destruction. One doctor in the area made sure that all the drug reps knew he would accept short dated (but not outdated, which would have been against policy for reps) samples for a free clinic he ran. Everyone I knew participated when they had short dated samples. While reps could not distribute outdated samples, doctors had much more latitude in how they dealt with them. It was one of those rare and wonderful situations that was good for patients, created good will for reps and was all completely within regulations.
I should say this was some years ago and regulations may have changed since then.