ISOSORBIDE MONONITRATe (eye-soe-sor'bide)
Ismo, Imdur, Monoket Classifications: nitrate vasodilator; Therapeutic: vasodilator; nitrate Prototype: Nitroglycerin Pregnancy Category: C
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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) 3060 mg every morning, may increase
up to 120 mg once daily after several days if needed (max: dose 240 mg)
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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 3060 min; sustained release 34 h.
Duration: Regular release 512 h; sustained release 12 h.
Metabolism: In liver by denitration and conjugation to inactive metabolites.
Elimination: Primarily by kidneys.
Half-Life: 45 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 (48 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.