Isosorbide mononitrate is 1,4:3,6-dianhydro-D-glucitol, 5-nitrate, an organic nitrate whose structural formula is:

and whose molecular weight is 191.14. The organic nitrates are vasodilators, active on both arteries and veins. Each Ismo tablet contains 20 mg of isosorbide mononitrate. The inactive ingredients in each tablet are colloidal silicon dioxide, D&C Yellow 10 Aluminum Lake, FD&C Yellow 6 Aluminum Lake, hydroxypropyl methylcellulose, lactose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, polysorbate 20, povidone, sodium starch glycolate, titanium dioxide and hydroxypropyl cellulose.

Last updated on RxList: 4/13/2009

Ismo tablets are indicated for the prevention 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.

(SEE INDICATIONS AND USAGE)

The recommended regimen of Ismo tablets is 20 mg (one tablet) twice daily, with the two doses given 7 hours apart. For most patients, this can be accomplished by taking the first dose on awakening and the second dose 7 hours later. Dosage adjustments are not necessary for elderly patients or patients with altered renal or hepatic 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 dosing regimen for Ismo tablets provides a daily nitrate-free interval to avoid the development of this tolerance. As also noted under CLINICAL PHARMACOLOGY, well-controlled studies have shown that tolerance to Ismo tablets is avoided when using the twice-daily regimen in which the two doses are given 7 hours apart. This regimen has been shown to have antianginal efficacy beginning 1 hour after the first dose and lasting at least 5 hours after the second dose. The duration (if any) of antianginal activity beyond 12 hours has not been studied; large controlled studies with other nitrates suggest that no dosing regimen should be expected to provide more than about 12 hours of continuous antianginal efficacy per day.

In clinical trials, Ismo tablets have been administered in a variety of regimens. Single doses less than 20 mg have not been adequately studied, while single doses greater than 20 mg have demonstrated no greater efficacy than doses of 20 mg.

Ismo (isosorbide mononitrate) tablets, 20 mg, are available in bottles of 100 (NDC 67857-702-01). Each orange, round, film-coated tablet is engraved "ISMO 20" on one side and scored on the reverse side.

Store at 20 - 25° C (68 -77° F) [See USP Controlled Room Temperature]. Dispense in tight container.

Manufactured by: West-ward Pharmaceutical Corp. Eatontown, NJ 07724. Manufactured for: Reddy Pharmaceuticals, LLC. Bridgewater, NJ 08807

Last updated on RxList: 4/13/2009

The table below shows the frequencies of the adverse reactions observed in more than 1% of the subjects (a) in 6 placebo-controlled domestic studies in which patients in the active-treatment arm received 20 mg of isosorbide mononitrate twice daily, and (b) in all studies in which patients received isosorbide mononitrate in a variety of regimens. In parentheses, the same table shows the frequencies with which these adverse reactions led to discontinuation of treatment. Overall, 11% of the patients who received isosorbide mononitrate in the six controlled U.S. studies discontinued treatment because of adverse reactions. Most of these discontinued because of headache. "Dizziness" and nausea were also frequently associated with withdrawal from these studies.

Frequency of Adverse Reactions (Discontinuations)*
	6 Controlled Studies		92 Clinical Studies
Dose	Placebo	20 mg	(varied)
Patients	204	219	3344
Headache	9% (0%)	38% (9%)	19% (4.3%)
Dizziness	1% (0%)	5% (1%)	3% (0.2%)
Nausea, Vomiting	< 1% (0%)	4% (3%)	2% (0.2%)
*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: angina pectoris, arrhythmias, atrial fibrillation, hypotension, palpitations, postural hypotension, premature ventricular contractions, supraventricular tachycardia, syncope.

Dermatologic: pruritus, rash.

Gastrointestinal: abdominal pain, diarrhea, dyspepsia, tenesmus, tooth disorder, vomiting.

Genitourinary: dysuria, impotence, urinary frequency.

Miscellaneous: asthenia, blurred vision, cold sweat, diplopia, edema, malaise, neck stiffness, rigors.

Musculoskeletal: arthralgia.

Neurological: agitation, anxiey, confusion, dyscoordination, hypoesthesia, hypokinesia, increased appetite, insomnia, nervousness, nightmares.

Respiratory: bronchitis, pneumonia, upper-respiratory tract infection.

Extremely rarely, ordinary doses of organic nitrates have caused methemoglobinemia in normal-seeming patients; for futher discussion of its diagnosis and treatment see under OVERDOSAGE.

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.

Last updated on RxList: 4/13/2009

Amplification of the vasodilatory effects of Ismo 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 hemo-dynamic monitoring must be used to avoid the hazards of hypotension and tachycardia.

General

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. 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.

Carcinogenesis, Mutagenesis, Impairment of Fertility:

No carcinogenic effects were observed in mice exposed to oral isosorbide mononitrate for 104 weeks at doses of up to 900 mg/kg/day (102 X the human exposure comparing body surface area). Rats treated with 900 mg/kg/day for 26 weeks (225 X the human exposure comparing body surface area) and 500 mg/kg/day for the remaining 95 to 111 weeks (males and females, respectively) showed no evidence of tumors. No mutagenic activity was seen in a variety of in vitro and in vivo assays. No adverse effects on fertility were observed when isosorbide mononitrate was administered to male and female rats at doses of up to 500 mg/kg/day (125 X the human exposure comparing body surface area).

Pregnancy Category C

Isosorbide mononitrate has been shown to be associated with stillbirths and neonatal death in rats receiving 500 mg/kg/day of isosorbide mononitrate (125 X the human exposure comparing body surface area). At 250 mg/kg/day, no adverse effects on reproduction and development were reported. In rats and rabbits receiving isosorbide mononitrate at up to 250 mg/kg/day, no developmental abnormalities, fetal abnormalities, or other effects upon reproductive performance were detected; these doses are larger than the maximum recommended human dose by factors between 70 (body-surface-area basis in rabbits) and 310 (body-weight basis, either species). In rats receiving 500 mg/kg/day, there were small but statistically significant increases in the rates of prolonged gestation, prolonged parturition, stillbirth, and neonatal death; and there were small but statistically significant decreases in birth weight, live litter size, and pup survival.

There are no adequate and well-controlled studies in pregnant women. Isosorbide mononitrate should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Nursing Mothers

It is not known whether isosorbide mononitrate is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when isosorbide mononitrate is administered to a nursing woman.

Pediatric Use

Safety and effectiveness of isosorbide mononitrate in pediatric patients have not been established.

Geriatric Use

Clinical studies of Ismo 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. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, although age, renal, hepatic or cardiac dysfunction do not appear to have a clinically significant effect on the clearance of Ismo®.

Last updated on RxList: 4/13/2009

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 doses of 2000 mg/kg and 3000 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. In particular, dialysis is known to be ineffective in removing isosorbide mononitrate from the body. 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 it probably could also occur as a side effect of isosorbide mononitrate. Certainly nitrate ions liberated during metabolism of isosorbide mononitrate can oxidize hemoglobin into methemoglobin. Even in patients totally without cytochrome b5 reductase activity, however, and even assuming that the nitrate moiety of isosorbide mononitrate is quantitatively applied to oxidation of hemoglobin, about 2 mg/kg of isosorbide mononitrate should be required before any of these patients manifests clinically significant ( > 10%) methemoglobinemia. In patients with normal reductase function, significant production of methemoglobin should require even larger doses of isosorbide mononitrate. In one study in which 36 patients received 2 to 4 weeks of continuous nitroglycerin therapy at 3.1 to 4.4 mg/hr (equivalent, in total administered dose of nitrate ions, to 7.8 to 11.1 mg of isosorbide mononitrate per hour), the average methemoglobin level measured was 0.2%; this was comparable to that observed in parallel patients who received placebo. Notwithstanding these observations, there are case reports of significant methemoglobinemia in association with moderate overdoses of organic nitrates. None of the affected patients had been thought to be unusually susceptible.

Methemoglobin levels are available from most clinical laboratories. The diagnosis should be suspected in patients who exhibit signs of impaired oxygen delivery despite adequate cardiac output and adequate arterial pO2. Classically, methemoglobinemic blood is described as chocolate brown, without color change on exposure to air. When methemoglobinemia is diagnosed, the treatment of choice is methylene blue, 1 to 2 mg/kg intravenously.

Allergic reactions to organic nitrates are extremely rare, but they do occur. Isosorbide mononitrate is contraindicated in patients who are allergic to it.

Last updated on RxList: 4/13/2009

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, due to its nitric oxide metabolite, is direct relaxation of vascular smooth muscle. The result is 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 continu-ously 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 Ismo 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 same twice-daily regimen of Ismo 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

In humans, isosorbide mononitrate is not subject to first pass metabolism in the liver. The absolute bioavailability of isosorbide mononitrate from Ismo tablets is nearly 100%. Maximum serum concentrations of isosorbide mononitrate are achieved 30 to 60 minutes after ingestion of Ismo. The volume of distribution of isosorbide mononitrate is approximately 0.6 L/kg, and less than 4% is bound to plasma proteins. It is cleared from the serum by denitration to isosorbide; glucuronidation to the mononitrate glucuronide; and denitration/hydration to sorbitol. None of these metabolites is vasoactive. Less than 1% of administered isosorbide mononitrate is eliminated in the urine. The overall elimination half-life of isosorbide mononitrate is about 5 hours; the rate of clearance is the same in healthy young adults , in patients with various degrees of renal, hepatic, or cardiac dysfunction, and in the elderly. In a single-dose study, the pharmacokinetics of isosorbide mononitrate were dose-proportional up to at least 60 mg.

Clinical Trials

Controlled trials of single doses of Ismo tablets have demonstrated that antianginal activity is present about 1 hour after dosing, with peak effect seen from 1 to 4 hours after dosing. In placebo-controlled trials lasting 2 to 3 weeks, Ismo tablets were administered twice daily, in asymmetric regimens (with interdosing intervals of 7 and 17 hours) designed to avoid tolerance. One trial tested doses of 10 mg and 20 mg; one trial tested doses of 20 mg, 40 mg, and 60 mg; and three trials tested only doses of 20 mg. In each trial, the subjects were persons with known chronic stable angina, and the primary measure of efficacy was exercise tolerance on a standardized treadmill test. After initial dosing and for at least 3 weeks, exercise tolerance in patients treated with Ismo 20 mg tablets was significantly greater than that seen in patients treated with placebo, although there was some attenuation of effect with time. Treatment with Ismo tablets was superior to placebo for at least 12 hours after the first dose (i.e., 5 hours after the second dose) of each day. Significant tolerance and rebound phenomena were not observed. The 10-mg dose was not unequivocally superior to placebo, while the effect of the 40-mg dose was similar to that of the 20-mg dose. The 60-mg dose appeared to be less effective, and it was associated with a rebound phenomenon (early-morning worsening).

Last updated on RxList: 4/13/2009

Patients should be told that the antianginal efficacy of Ismo tablets can be maintained by carefully following the prescribed schedule of dosing (two doses taken 7 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. 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's antianginal efficacy. Treatment with isosorbide mononitrate may be associated with lightheadedness 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.

Last updated on RxList: 4/13/2009

IMPORTANT NOTE: This is a summary and does not contain all possible information about this product. For complete information about this product or your specific health needs, ask your health care professional. Always seek the advice of your health care professional if you have any questions about this product or your medical condition. This information is not intended as individual medical advice and does not substitute for the knowledge and judgment of your health care professional. This information does not contain any assurances that this product is safe, effective, or appropriate for you.

ISOSORBIDE MONONITRATE - ORAL

(EYE-soe-SOR-bide MON-oh-NYE-trate)

COMMON BRAND NAME(S): ISMO, Monoket

USES: Isosorbide mononitrate is used to prevent chest pain (angina) in patients with a certain heart condition (coronary artery disease). This medication belongs to a class of drugs known as nitrates. It works by relaxing and widening blood vessels so blood can flow more easily to the heart.

This medication will not relieve chest pain once it occurs. It is also not intended to be taken just before physical activities (such as exercise, sexual activity) to prevent chest pain. Other medications may be needed in these situations. Consult your doctor for more details.

OTHER USES: This section contains uses of this drug that are not listed in the approved professional labeling for the drug but that may be prescribed by your health care professional. Use this drug for a condition that is listed in this section only if it has been so prescribed by your health care professional.

This medication may also be used with other drugs to improve the symptoms of heart failure (such as trouble breathing).

HOW TO USE: Take this medication by mouth, usually twice daily or as directed by your doctor. Take the first dose of the day when you wake up, then take the second dose 7 hours later. It is important to take the drug at the same times each day. Do not change the dosing times unless directed by your doctor.

Use this medication regularly to get the most benefit from it. Do not stop taking it without consulting your doctor. Some conditions may become worse when the drug is suddenly stopped. Your dose may need to be gradually decreased.

Although unlikely, when this medication is used for a long time, it may not work as well and may require different dosing. Tell your doctor if this medication stops working well (for example, you have worsening chest pain or it occurs more often).

SIDE EFFECTS: Headache, dizziness, lightheadedness, nausea, and flushing may occur as your body adjusts to this medication. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.

Headache is often a sign that this medication is working. Your doctor may recommend treating headaches with an over-the-counter pain reliever (such as acetaminophen, aspirin). If the headaches continue or become severe, tell your doctor promptly.

To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor immediately if any of these unlikely but serious side effects occur: fainting, fast/irregular/pounding heartbeat.

A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any of the following symptoms of a serious allergic reaction: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

Contact your doctor for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Food and Drug Administration (FDA) at 1-800-FDA-1088. In Canada, you may call Health Canada at 1-866-234-2345.

PRECAUTIONS: Before taking this medication, tell your doctor or pharmacist if you are allergic to it; or to similar drugs (such as nitroglycerin); or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: recent head injury.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: anemia, low blood pressure, loss of too much body water (dehydration), other heart problems (such as recent heart attack).

This drug may make you dizzy. Use caution while driving, using machinery, or doing any activity that requires alertness. Limit alcoholic beverages.

Before having surgery, tell your doctor or dentist that you are using this medication.

Older adults may be more sensitive to the side effects of this medication, especially dizziness and lightheadedness, which could increase the risk of falls.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

It is unknown if this medication passes into breast milk or if it may harm a nursing infant. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor or pharmacist first.

This drug should not be used with the following medications because very serious (possibly fatal) interactions may occur: drugs to treat erectile dysfunction (such as sildenafil, tadalafil, vardenafil).

If you are currently using any of these medications, tell your doctor or pharmacist before starting isosorbide mononitrate.

Before using this medication, tell your doctor or pharmacist of all prescription and nonprescription/herbal products you may use, especially of: rosiglitazone, certain drugs to treat migraine headaches (ergot alkaloids such as ergotamine), drugs that lower blood pressure (including alpha blockers such as tamsulosin).

This medication may interfere with certain laboratory tests (including blood cholesterol levels), possibly causing false test results. Make sure laboratory personnel and all your doctors know you use this drug.

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist.

OVERDOSE: If overdose is suspected, contact your local poison control center or emergency room immediately. US residents can call the US National Poison Hotline at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: slow heartbeat, vision changes, severe nausea/vomiting, sweating, cold/clammy skin, bluish fingers/toes/lips.

NOTES: Do not share this medication with others.

Laboratory and/or medical tests (such as blood pressure monitoring) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

Lifestyle changes such as dietary changes, exercise, and stopping smoking may help this drug work better. Talk to your doctor or pharmacist about lifestyle changes that might benefit you.

MISSED DOSE: If you miss a dose, take it as soon as you remember. If it is within 2 hours of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

STORAGE: Store at room temperature between 68-77 degrees F (20-25 degrees C) away from light and moisture. Do not store in the bathroom. Keep all medicines away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company for more details about how to safely discard your product.

MEDICAL ALERT: Your condition can cause complications in a medical emergency. For enrollment information call MedicAlert at 1-800-854-1166 (USA) or 1-800-668-1507 (Canada).

Information last revised September 2008 Copyright(c) 2008 First DataBank, Inc.