Read one pharmacist’s answer here.
Expiration dates were established in 1979 to ensure the safety and effectiveness of medications.
Medications that have been stored in their original containers under controlled conditions (not your medicine cabinet) retain much of their original effectiveness.
Medications for life-threatening conditions, like epinephrine pens for anaphylactic allergic reactions, should not be used after their expiration date. Tablets that are discolored, have a strong odor or discoloration should not be used. Liquids should not be cloudy. Preservatives in open bottles of eye drops or nasal sprays may no longer be effective.