Nitrates are a special group of drugs that are important mainly for internal medicine, particularly for cardiology.
Nitrates get into the blood stream and release nitric oxide (NO). This substance has an important effect on muscle cells in arterial walls and causes their dilation. Dilation of the arteries allows better blood flow, reduces arterial resistance and reduces blood pressure.
The above effects are used in the therapy of angina pectoris and high blood pressure. Angina pectoris is a very unpleasant chest pain, which occurs during physical exercise and disappears at rest. It is caused by worse blood supply of the heart due to narrowed coronary arteries. Nitrates dilate the coronary arteries, improve the blood supply of heart and lead to pain disappearance. The nitrates can be also used in acute myocardial infarction, when the patient does not have low blood pressure. The treatment of high blood pressure is similar. The nitrates dilate the arteries and blood pressure drops. However, we rather use nitrates to solve acute hypertension.
There are many used substances; they may be administered in oral, spray or intravenous form. Their use depends on the actual situation and indication.
Therapy of acute angina pectoris or myocardial infarction
In this case, we prefer sublingual tablet or spray, which is applied during an attack of pain. Te nitrate quickly absorbs through the oral mucosa. This ensures rapid effect and disappearance of the pain. This group of nitrates includes, for example, a substance known as isosorbide dinitrate and glyceryl trinitrate.
Use of nitrates in prevention of pain in angina pectoris
This indication prefers oral tablets with a slow releasing of the active substance. The tablets are taken regularly. Typical used substance is isosorbide mononitrate.
Nitrate administration in high blood pressure
In this case, we prefer nitrate forms adapted for intravenous administration. It can be applied in infusion or by a special medical pump. Used active substance is for example the already mentioned isosorbide dinitrate, or glycerol trinitrate.
Excessive effect of the nitrates may cause hypotension with all its consequences including fatigue, dizziness and fainting. In such case, the dose of nitrates must be reduced. In addition, the nitrates may cause headaches and redness of the face (by dilation of facial arteries). We must also take into account the fact that long-term use of nitrates in angina pectoris has no impact on the mortality of patients. Mortality in patients receiving nitrate is virtually indistinguishable from patients who do not use nitrate and the nitrate “only” reduces the frequency of chest pain attacks and improves the patient's life quality.
Nitrates are valuable drugs that have great use in cardiac patients with angina pectoris and in conditions with acute hypertension. However, when treating the angina pectoris, we should take the nitrates as symptomatic drugs that do not solve the causes of angina pectoris, nor improve the survival of patients.