Isosorbide

INDICATIONS AND USAGE 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.

CLINICAL PHARMACOLOGY Isosorbide mononitrate is the major active metabolite of isosorbide dinitrate (ISDN), and most of the clinical activity of the dinitrate is attributable to the mononitrate. The principal pharmacological action of isosorbide mononitrate is relaxation of vascular smooth muscle and consequent dilatation of peripheral arteries and veins, especially the latter. Dilation of the veins promotes peripheral pooling of blood and decreases venous return to the heart, thereby reducing left ventricular end-diastolic pressure and pulmonary capillary wedge pressure (preload). Arteriolar relaxation reduces systemic vascular resistance, systolic arterial pressure, and mean arterial pressure (afterload). Dilatation of the coronary arteries also occurs. The relative importance of preload reduction, afterload reduction and coronary dilatation remains undefined. Pharmacodynamics Dosing regimens for most chronically used drugs are designed to provide plasma concentrations that are continuously greater than a minimally effective concentration. This strategy is inappropriate for organic nitrates. Several well-controlled clinical trials have used exercise testing to assess the antianginal efficacy of continuously-delivered nitrates. In the large majority of these trials, active agents were indistinguishable from placebo after 24 hours (or less) of continuous therapy. Attempts to overcome tolerance by dose escalation, even to doses far in excess of those used acutely, have consistently failed. Only after nitrates have been absent from the body for several hours has their antianginal efficacy been restored. The drug-free interval sufficient to avoid tolerance to isosorbide mononitrate has not been completely defined. In the only regimen of twice-daily isosorbide mononitrate that has been shown to avoid development of tolerance, the two doses of isosorbide mononitrate tablets are given 7 hours apart, so there is a gap of 17 hours between the second dose of each day and the first dose of the next day. Taking account of the relatively long half-life of isosorbide mononitrate this result is consistent with those obtained for other organic nitrates. The asymmetric twice-daily regimen of isosorbide mononitrate tablets successfully avoided significant rebound/withdrawal effects. The incidence and magnitude of such phenomena have appeared, in studies of other nitrates, to be highly dependent upon the schedule of nitrate administration. Pharmacokinetics Isosorbide mononitrate is rapidly and completely absorbed from the gastrointestinal tract. In humans, isosorbide mononitrate is not subject to first pass metabolism in the liver. The absolute bioavailability of isosorbide mononitrate from isosorbide mononitrate tablets is nearly 100%. Peak plasma concentrations usually occur in about 30-60 minutes. Isosorbide mononitrate exhibits dose proportionality over the recommended dose range. Food does not significantly affect the absorption or bioavailability of isosorbi

DOSAGE AND ADMINISTRATION 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. Doses of 5 mg twice a day are clearly effective (effectiveness based on exercise tolerance) for only the first day of a twice-a-day (with doses 7 hours apart) regimen.

ADVERSE REACTIONS 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. Frequency Of Adverse Reactions (Discontinuations)* 6 Placebo-Controlled Studies Dose Placebo 5 mg 10 mg 20 mg Patients 160 54 52 159 Headache 6% (0%) 17% (0%) 13% (0%) 35% (5%) Fatigue 2% (0%) 0% (0%) 4% (0%) 1% (0%) Upper Respiratory Infection <1% (0%) 0% (0%) 4% (0%) 1% (0%) Pain <1% (0%) 4% (0%) 0% (0%) <1% (0%) Dizziness 1% (0%) 0% (0%) 0% (0%) 4% (0%) Nausea <1% (0%) 0% (0%) 0% (0%) 3% (2%) Increased Cough <1% (0%) 0% (0%) 2% (0%) <1% (0%) Rash 0% (0%) 2% (2%) 0% (0%) <1% (0%) Abdominal Pain <1% (0%) 0% (0%) 2% (0%) 0% (0%) Allergic Reaction 0% (0%) 0% (0%) 2% (0%) 0% (0%) Cardiovascular Disorder 0% (0%) 2% (0%) 0% (0%) 0% (0%) Chest Pain <1% (0%) 0% (0%) 2% (0%) <1% (0%) Diarrhea 0% (0%) 0% (0%) 2% (0%) 0% (0%) Flushing 0% (0%) 0% (0%) 2% (0%) 0% (0%) Emotional Lability 0% (0%) 2% (0%) 0% (0%) 0% (0%) Pruritus 1% (0%) 2% (2%) 0% (0%) 0% (0%) *Some individuals discontinued for multiple reasons. Other adverse reactions, each reported by fewer than 1% of exposed patients, and in many cases of uncertain relation to drug treatment, were: Cardiovascular: acute myocardial infarction, apoplexy, arrhythmias, bradycardia, edema, hypertension, hypotension, pallor, palpitations, tachycardia. Dermatologic: sweating. Gastrointestinal: anorexia, dry mouth, dyspepsia, thirst, vomiting, decreased weight. Genitourinary: prostatic disorder. Miscellaneous: amblyopia, back pain, bitter taste, muscle cramps, neck pain, paresthesia, susurrus aurium. Neurologic: anxiety, impaired concentration, depression, insomnia, nervousness, nightmares, restlessness, tremor, vertigo. Respiratory: asthma, dyspnea, sinusitis. Extremely rarely, ordinary doses of organic nitrates have caused methemoglobinemia in normal-seeming patients; for further discussion of its diagnosis and treatment see OVERDOSAGE . To report SUSPECTED ADVERSE REACTIONS, contact ANI Pharmaceuticals, Inc. at 1-855-204-1431 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

WARNINGS 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. If isosorbide mononitrate is used in these conditions, careful clinical or hemodynamic monitoring must be used to avoid the hazards of hypotension and tachycardia.

CONTRAINDICATIONS 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.

OVERDOSAGE 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 reduced ventilatory effort; diaphoresis, with the skin either flushed or cold and clammy; heart block and bradycardia; paralysis; coma; seizures and death. Laboratory determinations of serum levels of isosorbide mononitrate and its metabolites are not widely available, and such determinations have, in any event, no established role in the management of isosorbide mononitrate overdose. There are no data suggesting what dose of isosorbide mononitrate is likely to be life-threatening in humans. In rats and mice, there is significant lethality at oral doses of 1965 mg/kg and 2581 mg/kg, respectively. No data are available to suggest physiological maneuvers (e.g., maneuvers to change the pH of the urine) that might accelerate elimination of isosorbide mononitrate. Isosorbide mononitrate is significantly removed from the blood during hemodialysis. No specific antagonist to the vasodilator effects of isosorbide mononitrate is known, and no intervention has been subject to controlled study as a therapy of isosorbide mononitrate overdose. Because the hypotension associated with isosorbide mononitrate overdose is the result of venodilatation and arterial hypovolemia, prudent therapy in this situation should be directed toward an increase in central fluid volume. Passive elevation of the patient’s legs may be sufficient, but intravenous infusion of normal saline or similar fluid may also be necessary. The use of epinephrine or other arterial vasoconstrictors in this setting is likely to do more harm than good. In patients with renal disease or congestive heart failure, therapy resulting in central volume expansion is not without hazard. Treatment of isosorbide mononitrate overdose in these patients may be subtle and difficult, and invasive monitoring may be required. Methemoglobinemia Methemoglobinemia has been reported in patients receiving other organic nitrates, and