isosorbide mononitrate

Action

Promotes peripheral vasodilation and reduces preload and afterload, decreasing myocardial oxygen consumption and increasing cardiac output. Also dilates coronary arteries, increasing blood flow and improving collateral circulation.

Availability

isosorbide dinitrate

Capsules: 40 mg

Capsules (extended-release): 40 mg

Tablets: 2.5 mg, 5 mg, 10 mg, 20 mg, 30 mg, 40 mg

Tablets (chewable): 5 mg, 10 mg

Tablets (extended-release): 20 mg, 40 mg

Tablets (sublingual): 2.5 mg, 5 mg, 10 mg

isosorbide mononitrate

Tablets: 10 mg, 20 mg

Tablets (extended-release): 30 mg, 60 mg, 120 mg

Indications and dosages

➣ Treatment and prophylaxis in situations likely to provoke acute angina pectoris

Adults: 2.5 to 5 mg S.L. May repeat dose q 5 to 10 minutes for a total of three doses in 15 to 30 minutes.

➣ Prophylaxis of angina pectoris

Adults: 5 to 40 mg P.O. (dinitrate conventional tablets) two to three times daily. Or 5 to 20 mg (mononitrate conventional tablets) b.i.d. Or 30 to 60 mg (mononitrate extended-release tablets) once daily. After several days, dosage may be increased to 120 mg (given as single 120-mg tablet or two 60-mg tablets) once daily. Rarely, 240 mg/day (mononitrate extended-release tablets) may be needed.

Off-label uses

• Heart failure

Contraindications

• Hypersensitivity to drug

• Severe anemia

• Acute myocardial infarction

• Angle-closure glaucoma

• Concurrent sildenafil therapy

Precautions

Use cautiously in:

• head trauma, volume depletion

• elderly patients

• pregnant or breastfeeding patients

• children.

Administration

• Give oral form 30 minutes before or 1 to 2 hours after a meal. Make sure patient swallows tablets or capsules whole.

• Have patient wet S.L. tablet with saliva before placing it under tongue. To avoid tingling sensation, have him place tablet in buccal pouch.

Adverse reactions

CNS: dizziness, headache, apprehension, asthenia, syncope

CV: orthostatic hypotension, tachycardia, paradoxical bradycardia, rebound hypertension

EENT: sublingual burning (with S.L. route)

GI: nausea, vomiting, dry mouth, abdominal pain

Skin: flushing

Interactions

Drug-drug. Aspirin: increased isosorbide blood level and effects

Beta-adrenergic blockers, calcium channel blockers, phenothiazines: additive hypotension

Dihydroergotamine: antagonism of dihydroergotamine effects

Sildenafil: severe and potentially fatal hypotension

Drug-diagnostic tests. Cholesterol: decreased level

Methemoglobin, urine vanillylmandelic acid: increased levels

Patient monitoring

• Monitor ECG and vital signs closely, especially blood pressure.

See In suspected overdose, assess for signs and symptoms of increased intracranial pressure.

• Monitor arterial blood gas values and methemoglobin levels.

Patient teaching

• Teach patient to take oral drug 30 minutes before or 1 to 2 hours after a meal.

• Inform patient that drug may cause headache. Advise him to treat headache as usual and not to alter drug schedule. If headache persists, tell him to contact prescriber.

• Instruct patient to move slowly when sitting up or standing, to avoid dizziness or light-headedness from sudden blood pressure decrease.

• As appropriate, review all other significant adverse reactions and interactions, especially those related to the drugs and tests mentioned above.