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Back one screen: left arrow Back to main menu: ESC NITRATES : CONTRAINDICATIONS and WARNINGS * Hypersensitivity to nitrates (rare). * Severe anemia (relative contraindication because vasodilation will further increase the heart rate and may increase the work of the heart). * Hypotension, especially in myocardial infarction (because it is suspected that further reduction in coronary perfusion pressure may worsen cardiac ischemia). * Brain injury, other conditions involving suspected increase in intracranial pressure (because vasodilators may further in- crease intracranial pressure). * Arcing may occur when cardioversion is performed on a patient with a transdermal nitroglycerine patch on the chest. Such patches should be removed before applying the shock.(Warning) * Syncope. (Warning) Postural hypotension may occasionally be sufficient to cause syncope. * Myocardopathy. (Warning) Nitrates may worsen angina in patients with hypertrophic cardiomyopathy. (PgDn key for more text) ADVERSE REACTIONS AND OVERDOSE TOXICITY: Severe toxicity is rare, even when these drugs are abused as "recreational" (sex-enhancing) agents. * CNS: A throbbing headache is common, especially if no tolerance to the drug is present. Dizziness (probably due to orthostatic hypotension) is often reported after large doses. * CV: Mild-to-moderate orthostatic hypotension, caused by peripheral venodilatation, is common. It is readily relieved by sitting or lying down. Tachycardia is a common reflex response to the hypotension. Gross overdosage may induce severe hypotension, especially in susceptible individuals, eg, those with hypovolemia. Associated symptoms, which are usually transient, include dizziness, syncope, sweating, tachycardia, nausea, and vomiting. Treatment, if necessary, is by administration of vasoconstrictors, usually sympathomimetics. * GI: Nausea and rarely, vomiting, may occur with ordinary therapeutic use. Sublingual and buccal preparations often cause a burning or tingling sensation in the mouth, and this has been assumed to constitute a test of the "activity" of the preparation. It is not a reliable test. (PgDn key for more text) * Skin: Hypersensitivity reactions may be induced by transdermal preparations, perhaps caused by the vehicle and adhesives that are present. * Methemoglobinemia: Nitrites may cause methemoglobinemia at moderate doses and this effect is common with overdoses. This may be hazardous, especially in anemic individuals. It is used therapeutically as an antidote in cyanide poisoning. Nitrates rarely if ever cause methemoglobinemia, except in unweaned infants. Severe methemoglobinemia is associated with pseudocyanosis, acidosis, and other signs of tissue hypoxia. Treatment is by slow IV administration of methylene blue, 1-2 mg/kg. INTERACTIONS * Hypotensive agents: Because they lack direct autonomic and me- tabolic effects, the only significant interaction of the nitrates is with other hypotensive agents, with which they have additive or superadditive effects. (Home to return to top of file)

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