I sent a colleague to see a hotel guest perhaps thirty years ago. He didn’t carry a bag as well stocked as mine but took some drug samples from the office. He gave one out. Later the guest noticed that its expiration date was past. His anger, when he phoned me, remains a vivid memory.
Commercial prescription drugs are probably OK for years after they expire, but we don’t give them out. My bottle of nasal spray has an expiration date, and it’s pure salt water. When my aspirin expired, I kept it around.
My lawyer has tapped me on the shoulder and warned me to add that this is my personal opinion, that I have no special pharmaceutical expertise, and that you must never take an expired drug.