Coronary artery atherosclerotic heart disease is the most common type of organ lesion caused by atherosclerosis and a common disease in the middle-aged and elderly population, seriously endangering human health. There are five main clinical types of coronary heart disease, namely asymptomatic myocardial ischemia, angina pectoris, myocardial infarction, ischemic cardiomyopathy, and sudden cardiac death. In clinical practice, they are also often divided into stable coronary heart disease and acute coronary syndromes. Most patients who visit the clinic know that when angina attacks, the emergency medication is sublingual nitroglycerin for quick relief of angina symptoms. Is nitroglycerin suitable for all people and what are the precautions? This article will provide detailed answers to this question. The main role of nitroglycerin: Nitroglycerin is a century-old drug, which has been used in clinical practice for 150 years, and is a classic drug to relieve angina. The main mechanism of nitroglycerin to control angina attacks is the release of nitric oxide in the body, which can make the increase of cyclic guanosine monophosphate in vascular smooth muscle and other tissues, and this substance can well regulate vasodilation. Further, by dilating coronary arteries and increasing coronary blood supply, the effect of relieving angina symptoms is achieved. In addition, it can also reduce the burden on the heart by dilating other arteries and veins, causing a decrease in peripheral vascular resistance and reducing the anterior and posterior loads on the heart. Among all drugs, nitroglycerin is a potent anti-anginal drug and is a necessary medicine for first aid in the event of coronary heart disease. In addition to angina emergency, nitroglycerin can also be used to temporarily lower blood pressure and treat chronic heart failure. Second, the correct way to take nitroglycerin: Generally speaking, nitroglycerin is mainly used for first aid, so most cases only appear in critical moments. After the onset of symptoms immediately contain a tablet, after 5 minutes after the effect can not be seen to contain another, up to 3 consecutive applications (angina symptoms generally do not exceed 30 minutes, if still can not relieve, then you should call the emergency). Sublingual nitroglycerin, 1 to 2 minutes to take effect, the effect time can be maintained for 20-30 minutes. Oral administration is undesirable because of its long onset time and poor efficacy. After containing nitroglycerin under the tongue, there will be a burning sensation, which is also a manifestation of the effectiveness of the drug. Third, the adverse reactions of nitroglycerin: taking nitroglycerin common adverse reactions are vasodilatory headache, dizziness, facial flushing, nausea, vomiting, abdominal pain, blurred vision, reflex tachycardia, postural hypotension, accelerated breathing, and even syncope. If nitroglycerin is taken in excess, mental confusion, depression, mania, cyanosis, coronary artery spasm, etc., and even respiratory paralysis and death by asphyxiation may also occur. The adverse reaction of allergy caused by nitroglycerin is rare, but anaphylactic shock can occur in serious cases, which is extremely dangerous if not treated in time. So you need to pay attention when taking nitroglycerin. Fourth, the use of nitroglycerin precautions: not long-term application of nitroglycerin sublingual and intravenous infusion can only be used as an emergency application, should not be taken for a long time. Long-term use of isosorbide mononitrate or extended-release tablets can be taken orally. However, it should be noted that long-term oral nitrates can also produce drug resistance; do not apply a large number of patients taking a large dose of nitroglycerin can further aggravate or even induce angina pectoris, therefore, if the first aid is ineffective or the effect is not good, you can take one more sublingual tablet, the total number of tablets up to 3. Overdose can cause severe hypotension, tachycardia, bradycardia, conduction block, palpitations, circulatory failure leading to death, syncope, persistent throbbing headache, vertigo, visual disturbance, increased intracranial pressure, paralysis and coma with convulsions, flushing and sweating, nausea and and vomiting, abdominal cramps and diarrhea, dyspnea and methemoglobinemia, etc. Five, which angina patients to prohibit or caution with nitroglycerin: 1, hypotensive patients hypotensive patients or patients with normally low blood pressure should use nitroglycerin with caution, because nitroglycerin will make the blood pressure drop even lower. It is especially likely to occur when there is a sudden change in body position. It is contraindicated in early myocardial infarction (with severe hypotension and tachycardia), especially in patients with acute inferior posterior wall myocardial infarction and right ventricular myocardial infarction. 2, hypertrophic obstructive cardiomyopathy patients nitroglycerin will further aggravate the left ventricular outflow tract obstruction in patients with this disease, and even cause syncope and sudden death, should be avoided as far as possible. 3, cerebral hemorrhage, intracranial pressure increase patients nitroglycerin also dilates cerebral vessels, which can aggravate the original condition, so cerebral hemorrhage, intracranial pressure increase patients should be careful with nitroglycerin. 4, glaucoma patients for glaucoma patients, especially primary angle-closure glaucoma without surgery, the application of nitroglycerin will further increase intraocular pressure, eye pain, and even more serious reactions. 5, Severe anemia patients with severe anemia will aggravate the clinical symptoms after applying nitroglycerin. 6, patients who are applying sildenafil because sildenafil (Viagra) can increase the antihypertensive effect of nitrate drugs, so the two drugs should not be taken together to avoid serious hypotension or even sudden death.