In symptomatic patients, angina is relieved by correction of the myocardial oxygen supply and demand imbalance. β-blockers and calcium channel blockers reduce myocardial oxygen demand by reducing heart rate and contractility, thereby reducing myocardial oxygen consumption. β-blockers have proven efficacy in CAD patients with a prior myocardial infarction, hypertension, or reduced left ventricular systolic function. In addition, β-blockers are usually well tolerated and there are few contraindications to their use.

Calcium channel blockers decrease angina symptoms by dilating the coronary arteries, thereby increasing myocardial blood flow. Calcium channel blockers are well tolerated by most patients and are associated with fewer side effects than β-blockers or nitrates. The most common side effect of calcium channel blockers is peripheral edema due to changes in capillary hydrostatic pressure. However, observational studies have raised concerns about the long term safety of calcium channel blockers, especially the short-acting preparations. In addition, these agents do little to arrest the progression of disease and have not been shown to increase longevity. The newer dihydropyridine calcium channel blockers have few negative inotropic effects and can be used in patients with reduced left ventricular performance. Cardiac conduction abnormalities may be potentiated when nondihydropyridine calcium channel blockers and β-blockers are used in combination.

Agents that affect loading conditions lower oxygen demand via a reduction in myocardial wall stress. These include nitrates, which reduce preload, and antihypertensive agents, which reduce afterload. Nitrates reduce angina symptoms primarily by peripheral venodilation, decreasing venous return and myocardial wall tension. Nitrates also have a coronary artery dilating effect. Nitroglycerin has mild antithrombotic and antiplatelet effects in patients with stable angina. Although nitrates are effective in treating angina, tolerance to these agents may develop. To avoid tolerance, patients should spend at least 8 hours daily (usually overnight) free of nitrates.

Nitrates should not be used in patients receiving a phosphodiesterase type 5 inhibitor (sildenafil, vardenafil, tadalafil). Coadministration of a phosphodiesterase type 5 inhibitor and a nitrate can cause life-threatening hypotension. Patients who take a phosphodiesterase type 5 inhibitor should not be given nitrates for at least 24 hours. In patients who take a longer-acting phosphodiesterase inhibitor (e.g., tadalafil), nitrates should be avoided for at least 48 hours.

Recommendations regarding major drug therapy in patients with chronic stable angina are summarized in Table 3.

©2007. American College of Physicians. All Rights Reserved. This material has been printed from the MKSAP^®14 program by the American College of Physicians. This application is licensed only for individual use and in accordance with terms defined by the owner upon initial use. For information about the product or to order, please visit www.acponline.org/catalog/mksap/14/.