Isosorbide nitrate extended-release tablets can be taken before or after meals, according to the drug instructions suggest that there is no clear regulation needs to be taken before or after meals. 1. Indications: This drug is mainly used for the prevention of angina pectoris, long-term treatment of coronary heart disease and treatment of persistent angina pectoris after myocardial infarction. 2. Adverse reactions: in the initial period of taking the drug, the symptoms of headache may appear, with the continuous use of the drug, the symptoms can disappear. Some patients may also experience nausea, drowsiness, hypotension and other symptoms. After continuous use of the drug, the symptoms will basically disappear gradually. 3. Contraindication: This drug is contraindicated in patients with severe cerebral arteriosclerosis, acute cardiac infarction, hypertrophic obstructive heart disease, hypotension, shock, glaucoma. 4. Precautions: this drug can not be used for acute attacks of angina pectoris; postural circulatory dysregulation should be used with caution; acute cardiac infarction with ventricular filling pressure should be used with caution; pregnant women, lactating women, children and the elderly should be careful with this drug. For patients, the specific way of taking the drug and related precautions and contraindications, must follow the doctor’s instructions.