Isosorbide Mononitrate

Trade Names:
ISMO
- Tablets 20 mg

Trade Names:
Imdur
- Tablets, extended-release 60 mg
- Tablets, extended-release 120 mg

Trade Names:
Monoket
- Tablets 10 mg
- Tablets 20 mg

Pharmacology

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Relaxes vascular smooth muscle and dilation of peripheral arteries and veins.

Pharmacokinetics

Absorption

Absolute bioavailability is approximately 100%; T _max is 0.5 to 1 h. Food may delay rate but not extent of absorption from extended-release tablets.

Distribution

Vd is 0.6 to 0.7 L/kg; approximately 4% or 5% protein bound.

Metabolism

Primarily metabolized in the liver. Five inactive metabolites.

Elimination

96% of administered dose excreted in urine and about 1% in feces (extended release). Mean plasma t _½ is approximately 5 h.

Indications and Usage

Treatment ( Monoket only) and prevention of angina pectoris caused by coronary artery disease.

Unlabeled Uses

In combination with nadolol to prevent variceal bleeding.

Contraindications

Hypersensitivity or idiosyncratic reactions to nitrates or nitrites; allergy to organic nitrates.

Dosage and Administration

PO (oral tablets) 20 mg twice daily, given 7 h apart. PO (extended-release tablets) Initial : 30 or 60 mg daily. Maintenance : After several days may be increased to 120 mg/day; rarely, 240 mg/day may be required.

General Advice

• To minimize development of tolerance, ensure that daily dose-free interval is provided.
• Caution patients not to chew or crush extended-release tablets.

Storage/Stability

Store tablets and extended-release tablets at controlled room temperature (68° to 77°F). Protect extended-release tablets from moisture.

Drug Interactions

Severe hypotension and CV collapse may occur.

Increased nitrate concentration and actions.

Symptomatic orthostatic hypotension.

Increased systolic BP and decreased antianginal effects may develop.

Because the hypotensive effects of nitrates may be potentiated, concomitant use of any form of organic nitrates is contraindicated in patients receiving phosphodiesterase type 5 inhibitors.

Laboratory Test Interactions

May cause false report of reduced serum cholesterol with Zlatkis-Zak color reaction.

Adverse Reactions

Cardiovascular

Abnormal heart sound, abnormal Q wave, aggravated angina pectoris, arrhythmia, atrial arrhythmia, atrial fibrillation, bradycardia, bundle branch block, cardiac failure, CV disorder, extrasystole, heart murmur, hypertension, hypotension, intermittent claudication, leg ulcer, MI, migraine, palpitation, tachycardia, varicose vein, ventricular tachycardia (less than 5%); syncope (postmarketing).

CNS

Dizziness, headache (at least 5%); anxiety, asthenia, impaired concentration, confusion, decreased libido, depression, fatigue, emotional liability, hypoesthesia, insomnia, malaise, nervousness, neuritis, paranoia, paresis, paresthesia, ptosis, somnolence, tremor, vertigo (less than 5%).

Dermatologic

Acne, abnormal hair texture, flushing, increased sweating, pruritus, rash, skin nodule (less than 5%).

EENT

Abnormal vision, conjunctivitis, earache, nasal congestion, pharyngitis, photophobia, rhinitis, tinnitus, tympanic membrane perforation (less than 5%).

GI

Abdominal pain, constipation, diarrhea, dry mouth; dyspepsia, flatulence, gastric ulcer, gastritis, glossitis, hemorrhagic gastric ulcer, hemorrhoids, increased sputum, loose stools, melena, nausea, vomiting (less than 5%).

Genitourinary

Atrophic vaginitis, breast pain, impotence, polyuria, renal calculus, UTI (less than 5%).

Hematologic-Lymphatic

Hypochromic anemia, purpura, thrombocytopenia (less than 5%).

Hepatic

ALT and AST increases (less than 5%).

Metabolic-Nutritional

Hyperuricemia, hypokalemia (less than 5%).

Musculoskeletal

Arthralgia, back pain, frozen shoulder, muscle weakness, musculoskeletal pain; myalgia, myositis, rigors, tendon disorder, torticollis (less than 5%).

Respiratory

Bronchitis, bronchospasm, coughing, dyspnea, pneumonia, pulmonary infiltration, rales, sinusitis, upper respiratory infection (less than 5%).

Miscellaneous

Allergic reaction, bacterial infection, chest pain, edema, fever, flu-like symptoms, hot flashes, moniliasis, pain, viral infection (less than 5%).

Precautions

Pregnancy

Category C , Category B ( Monoket and extended release).

Lactation

Undetermined.

Children

Safety and efficacy not established.

Elderly

Dose selection should be cautious, usually starting at the lower end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and comorbidity.

Acute MI/CHF

Benefits of immediate- and extended-release isosorbide mononitrate not established; use in these settings not recommended because effects of isosorbide mononitrate are difficult to terminate rapidly.

Angina

May aggravate angina caused by hypertrophic cardiomyopathy.

Methemoglobinemia

High doses may produce methemoglobinemia, especially in patients with methemoglobin reductase deficiency.

Severe hypotension

May occur even with small doses, particularly with upright posture; use with caution in patients who are hypotensive or volume depleted; alcohol accentuates this reaction.

Tolerance

May develop with repeated use for prolonged periods of time; minimize tolerance by ensuring daily isosorbide mononitrate-free intervals are provided.

Overdosage

Symptoms

Air hunger, bloody diarrhea, colic, coma, confusion, death, diaphoresis with flushed or cold and clammy skin, dyspnea followed later by reduced ventilatory effort, heart block and bradycardia, increased intracranial pressure, methemoglobinemia, moderate fever, nausea, palpitations, paralysis, seizures, syncope, throbbing headache, vertigo, visual disturbances, vomiting.

Patient Information

• Advise patient to review the patient information leaflet carefully before starting therapy and to read and check for new information each time the medication is refilled.
• Review with patient and family the signs and symptoms of angina (eg, acute onset of pressure-like chest pain that may radiate down the left arm and/or into the neck or jaw, often associated with sweating and shortness of breath or difficulty breathing).
• Instruct patient not to change from one brand of medicine to another without consulting health care provider. Products manufactured by different companies may not be equally effective.
• Instruct patient using extended-release tablets to swallow whole and not to crush or chew.
• Ensure patient using isosorbide mononitrate has sublingual nitroglycerin available at all times. Ensure patient knows when and how to use sublingual nitroglycerin and what to do if angina pain worsens or fails to respond to sublingual nitroglycerin.
• Caution patient that antianginal effectiveness of isosorbide is strongly related to the dosing regimen and not to change the dose or frequency of administration, or stop taking, unless advised by health care provider.
• Advise patient that headaches are a common adverse reaction of therapy and are also a marker of antianginal effectiveness. Advise patient that acetaminophen can be used to relieve headache without reducing the medication's antianginal effectiveness. Caution patient not to reduce the dose or change the frequency of administration of isosorbide to avoid medication-induced headache.
• Advise patient to notify health care provider if angina symptoms increase in frequency or severity, or if there is a sudden increase in the frequency of use of sublingual nitroglycerin.
• Caution patient that medication may cause dizziness, light-headedness, or fainting, especially while standing or following consumption of alcohol.
• Caution patient to avoid sudden position changes to prevent orthostatic hypotension.
• Instruct patient to notify health care provider if any of the following occur: frequent episodes of dizziness or light-headedness; fainting; intolerable headache; episodes or sweating, nausea, and/or vomiting; any unusual or unexplained feeling or sensation.

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