<p>Severe hypotension, particularly with upright posture, may occur with even small doses of isosorbide mononitrate. This drug should therefore be used with caution in patients who may be volume depleted or who, for whatever reason, are already hypotensive. Hypotension induced by isosorbide mononitrate may be accompanied by paradoxical bradycardia and increased angina pectoris.<br />
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Nitrate therapy may aggravate the angina caused by hypertrophic cardiomyopathy. In industrial workers who have had long-term exposure to unknown (presumably high) doses of organic nitrates, tolerance clearly occurs. Chest pain, acute myocardial infarction, and even sudden death have occurred during temporary withdrawal of nitrates from these workers, demonstrating the existence of true physical dependence. The importance of these observations to the routine, clinical use of oral isosorbide mononitrate is not known.<br />
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Patients should be told that the antianginal efficacy of Isosorbide Mononitrate tablets can be maintained by carefully following the prescribed schedule of dosing (two doses taken seven hours apart). For most patients, this can be accomplished by taking the first dose on awakening and the second dose 7 hours later.<br />
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As with other nitrates, daily headaches sometimes accompany treatment with isosorbide mononitrate. In patients who get these headaches, the headaches are a marker of the activity of the drug. Patients should resist the temptation to avoid headaches by altering the schedule of their treatment with isosorbide mononitrate, since loss of headache may be associated with simultaneous loss of antianginal efficacy. Aspirin and/or acetaminophen, on the other hand, often successfully relieve isosorbide mononitrate-induced headaches with no deleterious effect on isosorbide mononitrate&rsquo;s antianginal efficacy.<br />
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Treatment with isosorbide mononitrate may be associated with light-headedness on standing, especially just after rising from a recumbent or seated position. This effect may be more frequent in patients who have also consumed alcohol.</p>