Acute myocardial infarction and its consequences are the main causes of despair and deaths across the world. Nitroglycerin remains the most effective drug for acute myocardial infarction and angina pectoris.
Nitroglycerin raises nitric oxide, which results in vasodilation and enhances blood flow to the myocardium. However, repeated use of nitroglycerin increases the user’s tolerance to the medication’s benefits within 12 to 24 hours. This article states the benefits, mode of action, modes of administration, and adverse effects of nitroglycerin.
Benefits of using nitroglycerin:
Nitroglycerin, also known as nitro or glyceryl trinitrate (GTN), is basically used for vasodilation and for providing relief from anginal chest pain in people with coronary artery diseases. The Food and Drug Administration (FDA) has approved nitroglycerin for providing quick relief from an attack of angina pectoris (chest pain) or to be given prophylactically before engaging in activities that may cause an attack. . Non-FDA-approved uses include treatment of congestive heart failure (CHF), chronic anal fissures, coronary artery spasm, and angina caused by cocaine use.
The most valuable effect of nitro is its ability to introduce vasodilation which results in enhanced flow of blood to the heart. The effects of nitro are also visible in systemic veins where the venodilator effect minimizes cardiac preload and further reduces the stress on the walls of the heart.
In the last 150 years, GTN has become the ideal treatment for patients who have a myocardial infarction, unstable angina pectoris, and cardiac arrest. The vasodilation capability of nitro has been long admired. Industry employees who were often exposed to high levels of organic nitrites complained of headaches at the start of the week which were relieved during the weekends. The workers suffering from angina pectoris or cardiac arrest noted relief during the working days but it reappeared again on weekends. It was found that these effects were caused by the vasodilatory action of GTN. This fact was detected by the physicians in time. The effect of nitrate tolerance was generally known as ‘Monday disease’ because over the weekend the workers lost their tolerance and when they were re-exposed on Monday, the vasodilation produced dizziness, headache, and increased heart rate. Unfortunately, the recurrence of the angina was known as ‘Sunday Heart Failures’.
Mode of action
Nitroglycerin relaxes the vascular smooth muscle, causing arteriolar and venous dilatation. It decreases cardiac preload. afterload, systolic and diastolic blood pressure, and systemic vascular resistance. While those decrease the work that the heart has to do, nitro also reduces coronary artery spasm. The decrease in cardiac work by nitroglycerin is considered to give most relief to anginal symptoms and contributes to arteriolar dilatation effects.
Nitroglycerin has a vasodilatory effect in both veins and arteries. However, most beneficial effectsare principally due to venodilation. Venodilation results in the pooling of blood inside the venous system, minimizing preload to the heart, decreasing cardiac work, and reducing symptoms of angina. Arterial vasodilation also contributes to the relief of anginal symptoms. Vasodilation of the coronary arteries causes increased flow of blood to the heart, increasing perfusion but it remains minimal as compared to the effects of venodilation.
The dose must be repeatedly administered every five minutes until anginal pain is relieved. If the patient still feels anginal pain even after 3 doses, immediate medical attention should be provided. The onset of the desired vasodilatory effects occurs within 1 to 3 minutes after administration with a maximum time of five minutes. Nitroglycerin is removed by metabolism in the liver within two to three minutes.
Nitroglycerin has many adverse effects which result from the vasodilatory effects of the medication. The most significant adverse effects of nitroglycerin are:
Nitrates can cause hypotension in some patients. Unfortunately, this results in nausea, vomiting, pallor, diaphoresis, and syncope even after receiving therapeutic doses.
Patients taking nitroglycerin sometimes suffer from skin conditions like exfoliative dermatitis, flushing, and drug rash. The patient may experience constant, severe, and throbbing headaches just after receiving the dose of nitroglycerin. The most dangerous adverse effect is syncope because it can result in falls and serious injuries.
From the findings, patients who continuously take GTN have the possibility of serious cardiac damage. For patients with right coronary artery occlusion and chest pain, right ventricular infarction must be ruled out before administering nitroglycerin because it causes venodilation and decreases preload. In some patients, a decrease in preload may result in serious hypotension causing cardiogenic shock.