Isosorbide Mononitrate

Isosorbide Mononitrate Tablets USP are indicated for the prevention and treatment of angina pectoris due to coronary artery disease. The onset of action of oral isosorbide mononitrate is not sufficiently rapid for this product to be useful in aborting an acute anginal episode.

• The recommended regimen of isosorbide mononitrate tablets is 20 mg twice daily, with the doses seven hours apart
• A starting dose of 5 mg (½ tablet of the 10 mg dosing strength) might be appropriate for persons of particularly small stature but should be increased to at least 10 mg by the second or third day of therapy
• Dosage adjustments are not necessary for elderly patients or patients with altered hepatic or renal function
• As noted above ( CLINICAL PHARMACOLOGY ), multiple studies of organic nitrates have shown that maintenance of continuous 24-hour plasma levels results in refractory tolerance
• The asymmetric (2 doses, 7 hours apart) dosing regimen for isosorbide mononitrate tablets provides a daily nitrate-free interval to minimize the development of tolerance
• As also noted under CLINICAL PHARMACOLOGY , well-controlled studies have shown that tolerance to isosorbide mononitrate tablets occurs to some extent when using the twice-daily regimen in which the two doses are given seven hours apart
• This regimen has been shown to have antianginal efficacy beginning one hour after the first dose and lasting at least seven hours after the second dose
• The duration (if any) of antianginal activity beyond fourteen hours has not been studied
• In clinical trials, isosorbide mononitrate has been administered in a variety of regimens and doses
• Doses above 20 mg twice a day (with the doses seven hours apart) have not been adequately studied. …

• Safety and effectiveness of isosorbide mononitrate
• In pediatric patients have not been established

Clinical studies of isosorbide mononitrate did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. …

• 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
• 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. …

• Isosorbide mononitrate is contraindicated in patients who are allergic to it
• Do not use isosorbide mononitrate in patients who are taking certain drugs for erectile dysfunction (phosphodiesterase inhibitors), such as sildenafil, tadalafil, or vardenafil
• Concomitant use can cause severe hypotension, syncope, or myocardial ischemia
• Do not use isosorbide mononitrate in patients who are taking the soluble guanylate cyclase stimulator riociguat
• Concomitant use can cause hypotension

Concomitant use of isosorbide mononitrate with phosphodiesterase inhibitors in any form is contraindicated (see CONTRAINDICATIONS ). Concomitant use of isosorbide mononitrate with riociguat, a soluble guanylate cyclase stimulator, is contraindicated (see CONTRAINDICATIONS ). The vasodilating effects of isosorbide mononitrate may be additive with those of other vasodilators. Alcohol, in particular, has been found to exhibit additive effects of this variety. Marked symptomatic orthostatic hypotension has been reported when calcium channel blockers and organic nitrates were used in combination. Dose adjustments of either class of agents may be necessary.

Amplification of the vasodilatory effects of isosorbide mononitrate by sildenafil can result in severe hypotension. The time course and dose dependence of this interaction have not been studied. Appropriate supportive care has not been studied, but it seems reasonable to treat this as a nitrate overdose, with elevation of the extremities and with central volume expansion. The benefits of isosorbide mononitrate in patients with acute myocardial infarction or congestive heart failure have not been established. Because the effects of isosorbide mononitrate are difficult to terminate rapidly, this drug is not recommended in these settings. …

Headache is the most frequent side effect and was the cause of 2% of all dropouts from controlled-clinical trials. Headache decreased in incidence after the first few days of therapy. The following table shows the frequency of adverse reactions observed in 1% or more of subjects in 6 placebo-controlled trials, conducted in the United States and abroad. The same table shows the frequency of withdrawal for these adverse reactions. In many cases the adverse reactions were of uncertain relation to drug treatment. …

Pregnancy Teratogenic Effects Reproduction studies performed in rats and rabbits at doses of up to 540 and 810 mg/kg/day, respectively, have revealed no evidence of harm to the fetus due to isosorbide mononitrate. There are, however, no adequate and well-controlled studies in pregnant women. …

Hemodynamic Effects The ill effects of isosorbide mononitrate overdose are generally the results of isosorbide mononitrate’s capacity to induce vasodilatation, venous pooling, reduced cardiac output, and hypotension. These hemodynamic changes may have protean manifestations, including increased intracranial pressure, with any or all of persistent throbbing headache, confusion, and moderate fever; vertigo; palpitations; visual disturbances; nausea and vomiting (possibly with colic and even bloody diarrhea); syncope (especially in the upright posture); air hunger and dyspnea, later followed by r …

Take it when you remember, unless it is nearly time for the next dose. Then skip the missed one. Never take two doses at once to make up for it. Check your leaflet, as some medicines are different.