Nitrate therapy for ischaemic heart disease

The beneficial effects on nitrates are related to a combination of coronary and non-coronary effects of the drugs. Patients with different forms of ischaemic heart disease may respond differently. For instance, in a patient with rest angina due to coronary artery spasm, nitrates will reverse or prevent coronary artery spasm. In contrast, the patient with severe coronary artery stenosis and reproducible angina during exercise, may obtain relief because nitrates decrease venous return, left ventricular size and left ventricular pressure, thus decreasing myocardial oxygen demands. Nitrates can be used to treat patients with chronic angina, unstable angina and myocardial infarction. In patients with chronic angina, oral nitrate preparations with sustained-release action have been shown to decrease the indices of myocardial oxygen demand for up to 12 h. In patients with unstable angina, intravenous nitrates usually relieve symptoms in patients refractory to oral therapy. In patients with acute myocardial infarction, early administration with intravenous nitrates may benefit patients as suggested by randomized prospective trials. Nitrate tolerance and nitrate dependence does not seem to be an important clinical problem. Perhaps this is related to the way the drug is given, i.e. intermittently. In some instances, however, when high doses are used or the drug is administered intravenously or by the transdermal route, constant levels of nitroglycerine may be attained and the patients may develop tolerance. Although nitrates are effective drugs, it is native to think that they will be used alone to manage the complex problems associated with ischaemic heart disease. Other than hypotension and adverse effects of the drug, there seems to be no contraindication to the combination of nitrates with calcium antagonists or beta blockers.