Thiazides frequently are still a first-choice therapy for hypertension, especially when cost and compliance are important. They are also effective in the elderly with isolated systolic hypertension. Diuretics are often still required in controlling severe hypertension when multiple classes of drugs at maximal doses are being used without complete success. Loop diuretics are effective in patients with renal failure, and in those with congestive heart failure or others in whom edema is a major complaint.
What are the indications for chronic nitrate therapy?
Nitrates are used to treat angina related to atherosclerotic coronary artery disease and coronary artery spasm. They also lessen symptoms of chronic congestive heart failure and, in combination with hydralazine, improve survival and delay progression of left ventricular dysfunction (though not as well as angiotensin-converting enzyme inhibitors).
How do nitrates achieve their antianginal affects?
Nitrates dilate epicardial coronary arteries and coronary resistance vessels. Atherosclerotic coronary arteries respond to nitroglycerin even in areas of significant stenosis. Collateral vessels also dilate. Both result in an increase in 02 delivery to ischemic myocardium. Nitrates also affect systemic arteries and veins. Venodilation, by reducing preload, decreases diastolic volume, wall stress, and 02 consumption. Dilatation of systemic arteries decreases myocardial (), consumption
by decreasing afterload. Angina is relieved as 02 delivery to ischemic regions is increased and 02 consumption is decreased. In coronary spasm, nitrates relieve angina by their direct ability to dilate epicardial vessels at the sites of spasm.
1By what additional mechanism may nitrates be beneficial in unstable angina or acute myocardial infarction?
Nitroglycerin has antiplatelet effects which inhibit thrombus formation. This antiplatelet effect may contribute to the improved survival seen when intravenous nitroglycerin is used during myocardial infarction, and it may decrease recurrent ischemic episodes in patients with unstable angina.