Ismo Information
Ismo (Isosorbide mononitrate) Description
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 (Isosorbide mononitrate) 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.
Ismo (Isosorbide mononitrate) 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, 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.
Ismo (Isosorbide mononitrate) Indications And Usage
Ismo (Isosorbide mononitrate) 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.
Ismo (Isosorbide mononitrate) Contraindications
Allergic reactions to organic nitrates are extremely rare, but they do occur. Isosorbide mononitrate is contraindicated in patients who are allergic to it.
Ismo (Isosorbide mononitrate) Warnings
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.
Ismo (Isosorbide mononitrate) Precautions
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.
Ismo (Isosorbide mononitrate) Adverse Reactions
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.
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 .
Ismo (Isosorbide mononitrate) Overdosage
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 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 b 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 pO. 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.
Ismo (Isosorbide mononitrate) Dosage And Administration (see Indications And Usage)
The recommended regimen of Ismo (Isosorbide mononitrate) 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 (), multiple studies of organic nitrates have shown that maintenance of continuous 24-hour plasma levels results in refractory tolerance. The dosing regimen for Ismo (Isosorbide mononitrate) tablets provides a daily nitrate-free interval to avoid the development of this tolerance.
As also noted under , well-controlled studies have shown that tolerance to Ismo (Isosorbide mononitrate) 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 (Isosorbide mononitrate) 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) How Supplied
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 (Isosorbide mononitrate) 20” on one side and scored on the reverse side.
Ismo (Isosorbide mononitrate) Manufactured By:
West-ward Pharmaceutical Corp.
Eatontown, NJ 07724
Manufactured for:
Reddy Pharmaceuticals, LLC
Bridgewater, NJ 08807
