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Query: UMLS:C0012833 (dizziness)
 9,689 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nitrate usage worldwide is on the increase as the indications for therapy expand. Present indications for nitrate therapy include chronic stable angina pectoris, unstable angina pectoris, complications of acute myocardial infarction, and 'unloading' therapy for acute and chronic congestive heart failure. Nitrates are also being used in the operating suite by anaesthesiologists to control systolic blood pressure during various surgical procedures. New nitrate delivery systems have recently become available which provide considerable dosing flexibility, further increasing the interest in this group of compounds. The dominant action of nitrates is a direct effect on vascular smooth muscle, producing vasodilation of the veins and arteries. These drugs decrease myocardial work by lowering systolic blood pressure, systemic vascular resistance, and reducing intracardiac dimensions. In addition, nitrates have a potent effect on cardiac preload as a result of systemic venodilatation. There is also some evidence that nitrates exert direct effects on the coronary circulation (vasodilatation of coronary arteries and coronary collateral vessels, and direct atherosclerotic stenosis dilatation). These actions may play a role in relieving myocardial ischaemia. Adverse sequelae of nitrate therapy are well known and serious adverse reactions are uncommon. Headache and dizziness are the most frequent side effects. Nitrate tolerance is a definite problem - present evidence indicates that long acting formulations, high doses, or frequent dosing regimens are particularly likely to induce vascular tolerance to nitrates. Consequently, provision of a nitrate-free interval has taken on increasing significance as a strategy to avoid tolerance. Nitrate delivery systems are numerous. Although availability varies from country to country, in most countries there are a wide variety of formulations of glyceryl trinitrate (nitroglycerin) available, including sublingual and oral tablets, oral spray, topical ointment as well as discs or patches for transdermal administration, a transmucosal tablet and an intravenous formulation. Similar formulations of isosorbide dinitrate, except buccal tablets, are available in some countries. Isosorbide 5-mononitrate, a potent metabolite of isosorbide dinitrate, is achieving increasing popularity as an antianginal drug. Optimum nitrate therapy requires a good understanding of the properties of the various formulations, particularly onset and duration of action and propensity to induce tolerance.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Glyceryl trinitrate (nitroglycerin) and the organic nitrates. Choosing the method of administration. 311 8

Nitrates are potent relaxers of vascular smooth muscle and act by dilating veins, arteries, and arterioles (especially at high doses). Their clinical effects have been considered to be dominantly related to peripheral actions: systemic venodilatation and a decrease in systemic vascular resistance, reducing the preload and afterload of the heart. Considerable experimental work confirms potent salutary effects on the coronary circulation. These drugs are readily absorbed across mucosal surfaces; they are available in multiple formulations, including sublingual, buccal, oral, and topical delivery systems. Nitrate administration should begin with low doses and increased to doses that are often higher than previously recommended until a specific clinical end point or limiting side effects occur. Organic nitrate esters are effective in the treatment of stable angina pectoris, unstable angina, coronary vasospastic syndromes, and in vasodilator therapy in severe congestive heart failure. The pathophysiology of these syndromes is reviewed with respect to the clinical actions of nitrates on the central and peripheral circulations. The side effects of nitrates include headache, dizziness, and nausea. Nitrate tolerance, a controversial subject, does not appear to be an important clinical problem. Using the guidelines presented in this review, nitrate therapy provides effective, inexpensive, well-tolerated therapy for many patients with cardiovascular disease.
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PMID:Nitroglycerin and long-acting nitrates in clinical practice. 640 16

Nitrates are very effective antianginal and anti-ischaemic agents. Provision of a long nitrate-free interval or low plasma nitrate levels prior to the morning dose prevents the loss of clinical efficacy by preventing the development of tolerance. However, side effects during nitrate therapy are common. Headache is the most common side effect of nitrates; often dose-related and reported by up to 82% of patients in placebo-controlled trials. Nearly 10% of patients are unable to tolerate nitrates due to disabling headaches or dizziness. In others, headaches are mild-to-moderate in severity and either resolve or diminish in intensity with continued nitrate therapy. Nitrate-induced hypotension is common, but often asymptomatic. In rare instances, nitrate-induced hypotension is severe and accompanied by marked slowing of the heart rate and syncope. Use of nitrates in patients who experience syncope after administration of nitrates is contraindicated. Nitrates rarely cause coronary steal and myocardial ischaemia. Nitrate rebound may occur and patients may experience nocturnal anginal episodes during intermittent therapy with nitroglycerin patches. Administration of nitrates is contraindicated with concomitant use of phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction, as combination therapy may lead to profound hypotension and even death. There are disturbing observational reports in the literature that continuous, prolonged use of nitrates may lead to increased mortality and recurrent myocardial infarctions. Large, randomised, placebo-controlled studies are needed to confirm or refute these reports; until then, the use of nitrates to treat angina is here to stay.
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PMID:Side effects of using nitrates to treat angina. 1690 56