These drugs also reduce systemic vascular resistance, of both veins and arteries but the veins to a greater extent. The decrease in the resistance of the arteries and veins decreases the myocardial oxygen demand, which also reduces myocardial oxygen demand. Nitroglycerin is a potent vasodilator that decreases myocardial oxygen demand by decreasing the hearts workload. Nitroglycerin should not be given if certain inhibitors such as sildenafil, tadalafil, or vardenafil have been taken within the previous 12 hours as the combination of the two could cause a serious drop in blood pressure. Treatments for angina are balloon angioplasty, in which the balloon is inserted at the end of a catheter and inflated to widen the arterial lumen. Stents to maintain the arterial widening are often used at the same time. Coronary bypass surgery involves bypassing constricted arteries with venous grafts. This is much more invasive than angioplasty. Calcium channel blockers (such as nifedipine (Adalat) and amlodipine), isosorbide mononitrate and nicorandil are vasodilators commonly used in chronic stable angina. A new therapeutic class, called If inhibitor, has recently been made available: Ivabradine provides heart rate reduction without affecting contractility leading to major anti-ischemic and antianginal efficacy. ACE inhibitors are also vasodilators with both symptomatic and prognostic benefit. Statins are the most frequently used lipid/cholesterol modifiers, which probably also stabilize existing atheromatous plaque. Low-dose aspirin decreases the risk of heart attack in patients with chronic stable angina, and was part of standard treatment.
Meta-analysis and systematic reviews have concluded that laboratory confirmed aspirin resistance confers increased rates of poorer outcomes in cardiovascular and neurovascular diseases. Although the majority of research conducted has surrounded cardiovascular and neurovascular, there is emerging research into the risk of aspirin resistance after orthopaedic surgery where aspirin is used for venous thromboembolism prophylaxis. Aspirin resistance in orthopaedic surgery, specifically after total hip and knee arthroplasties, is of interest as risk factors for aspirin resistance are also risk factors for venous thromboembolisms and osteoarthritis; the sequalae of requiring a total hip or knee arthroplasty. Some of these risk factors include obesity, advancing age, diabetes mellitus, dyslipidaemia and inflammatory diseases. Dosages
Adult aspirin tablets are produced in standardised sizes, which vary slightly from country to country, for example 300 mg in Britain and 325 mg (or 5 grains) in the United States. Smaller doses are based on these standards, e.g., 75 mg and 81 mg tablets. The 81-milligram (1+1⁄4-grain) tablets are commonly called "baby aspirin" or "baby-strength", because they were originally – but no longer – intended to be administered to infants and children. No medical significance occurs due to the slight difference in dosage between the 75 mg and the 81 mg tablets. The dose required for benefit appears to depend on a persons weight.