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ISOSORBIDE MONONITRATE

Medical Diagnosis and Drugs, Medications
ISOSORBIDE MONONITRATe
(eye-soe-sor'bide)
Ismo, Imdur, Monoket
Classifications: nitrate vasodilator;
Therapeutic: vasodilator; nitrate
Prototype: Nitroglycerin
Pregnancy Category: C

Availability

10 mg, 20 mg tablets; 30 mg, 60 mg, 120 mg sustained release tablets

Action

Isosorbide mononitrate is a long-acting metabolite of the coronary vasodilator isosorbide dinitrate. It decreases preload as measured by pulmonary capillary wedge pressure (PCWP), and left ventricular end volume and diastolic pressure (LVEDV), with a consequent reduction in myocardial oxygen consumption.

Therapeutic Effect

It is equally or more effective than isosorbide dinitrate in the treatment of chronic, stable angina. It is a potent vasodilator with antianginal and antiischemic effects.

Uses

Prevention of angina. Not indicated for acute attacks.

Contraindications

Hypersensitivity to nitrates; severe anemia; closed-angle glaucoma; recent MI; postural hypotension, head trauma, cerebral hemorrhage (increases intracranial pressure); pregnancy (category C). Extended form should not be used in patients with GI disease.

Cautious Use

Older adults, hypotension; lactation.

Route & Dosage

Prevention of Angina
Adult: PO Regular release (ISMO, Monoket) 20 mg b.i.d. 7 h apart; Sustained release (Imdur) 30–60 mg every morning, may increase up to 120 mg once daily after several days if needed (max: dose 240 mg)

Administration

Oral
  • Give first dose in morning on arising and second dose 7 h later with twice daily dosing regimen. Give in morning on arising with once daily dosing.
  • Store sustained release tablets in a tight container.

Adverse Effects (≥1%)

CNS: Headache, agitation, anxiety, confusion, loss of coordination, hypoesthesia, hypokinesia, insomnia or somnolence, nervousness, migraine headache, paresthesia, vertigo, ptosis, tremor. CV: Aggravation of angina, abnormal heart sounds, murmurs, MI, transient hypotension, palpitations. Hematologic: Hypochromic anemia, purpura, thrombocytopenia, methemoglobinemia (high doses). GI: Nausea, vomiting, dry mouth, abdominal pain, constipation, diarrhea, dyspepsia, flatulence, tenesmus, gastric ulcer, hemorrhoids, gastritis, glossitis. Metabolic: Hyperuricemia, hypokalemia. GU: Renal calculus, UTI, atrophic vaginitis, dysuria, polyuria, urinary frequency, decreased libido, impotence. Respiratory: Bronchitis, pneumonia, upper respiratory tract infection, nasal congestion, bronchospasm, coughing, dyspnea, rales, rhinitis. Skin: Rash, pruritus, hot flashes, acne, abnormal texture. Special Senses: Diplopia, blurred vision, photophobia, conjunctivitis.

Interactions

Drug: Alcohol may cause severe hypotension and cardiovascular collapse. Aspirin may increase nitrate serum levels. calcium channel blockers may cause orthostatic hypotension.

Pharmacokinetics

Absorption: Completely and rapidly absorbed from GI tract; 93% reaches systemic circulation. Onset: 1 h. Peak: Regular release 30–60 min; sustained release 3–4 h. Duration: Regular release 5–12 h; sustained release 12 h. Metabolism: In liver by denitration and conjugation to inactive metabolites. Elimination: Primarily by kidneys. Half-Life: 4–5 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor cardiac status, frequency and severity of angina, and BP.
  • Assess for and report possible S&S of toxicity, including orthostatic hypotension, syncope, dizziness, palpitations, light-headedness, severe headache, blurred vision, and difficulty breathing.
  • Lab tests: Monitor serum electrolytes periodically.

Patient & Family Education

  • Do not crush or chew sustained release tablets. May break tablets in two and take with adequate fluid (4–8 oz).
  • Do not withdraw drug abruptly; doing so may precipitate acute angina.
  • Maintain correct dosing interval with twice daily dosing.
  • Note: Geriatric patients are more susceptible to the possibility of developing postural hypotension.
  • Avoid alcohol ingestion and aspirin unless specifically permitted by physician.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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