Drugs can not be used after the expiration date, may not only be used in vain, but also a health hazard, delayed treatment of disease. For expired drugs, although some in the appearance of the naked eye to observe no obvious changes, but the internal changes already exist, its active ingredients to reduce, can not achieve the original therapeutic effect, harmful to the human body, can not play the original role, will delay the condition, aggravate the patient’s condition, affecting the treatment. For example, containing nitroglycerin can be used for acute attacks of stable angina, such as expiration date failure, may bring about serious myocardial infarction or aggravate the pain. Even if it has not expired, the drug itself may even break down with harmful impurities if the storage conditions are substandard when the drug is kept. Moisture and dehydration may be absorbed during long-term storage, and the medicine will not decompose when it enters the human body after absorbing moisture and dehydration. Therefore, the human body cannot absorb the effective ingredients. It is recommended to regularly check the spare medicines at home and dispose of them in time.