What is the dosing for Isosorbide mononitrate (IMN)?

From the Guidelines

Isosorbide mononitrate should be dosed at 20 mg twice daily for the management of angina, as this dosing regimen has been shown to provide effective symptom control while minimizing the risk of nitrate tolerance. According to the 2012 ACCF/AHA focused update incorporated into the ACCF/AHA 2007 guidelines for the management of patients with unstable angina/non-ST-elevation myocardial infarction 1, the recommended dosing for isosorbide mononitrate is 20 mg twice daily, with a duration of effect of 12 to 24 hours.

Key Considerations

• The medication works by releasing nitric oxide, causing vasodilation of coronary and peripheral vessels, which reduces cardiac preload and afterload, thereby decreasing myocardial oxygen demand.
• Patients should be monitored for orthostatic hypotension, especially when initiating therapy or increasing doses.
• The medication should not be abruptly discontinued as this may cause rebound angina.
• Concomitant use with phosphodiesterase inhibitors (like sildenafil) is contraindicated due to the risk of severe hypotension.

Dosing Regimens

• Immediate-release formulations: twice-daily dosing (with the second dose given 7 hours after the first) is recommended to prevent nitrate tolerance, with a nitrate-free interval of 10-14 hours overnight.
• Extended-release formulations: 60 to 240 mg once daily, which can provide a more convenient dosing regimen for patients while maintaining effective symptom control.

Side Effects

• Common side effects include headache, dizziness, and hypotension.
• Patients should be educated on the potential side effects and the importance of adhering to the prescribed dosing regimen to minimize the risk of adverse effects.

From the FDA Drug Label

The recommended starting dose of isosorbide mononitrate extended-release tablets, USP is 30 mg (given as a single 30 mg tablet or as 1/2 of a 60 mg tablet) or 60 mg (given as a single tablet) once daily. After several days, the dosage may be increased to 120 mg (given as a single 120 mg tablet or as two 60 mg tablets) once daily. Rarely, 240 mg may be required. The dosage of isosorbide mononitrate is as follows:

• Starting dose: 30 mg or 60 mg once daily
• Increased dose: 120 mg once daily after several days
• Maximum dose: rarely, 240 mg may be required The daily dose should be taken in the morning on arising 2.

From the Research

Isosorbide Mononitrate Dosing

• The dosing of isosorbide mononitrate is crucial in preventing nitrate tolerance, which can lead to a loss of anti-ischemic effects 3.
• Studies have shown that intermittent therapy with once-daily ingestion of high-dose sustained-release isosorbide dinitrate or isosorbide-5-mononitrate can prevent the development of tolerance 3, 4.
• A daily low-nitrate interval is required to prevent tolerance development, and a 12-h patch-free interval should prevent tolerance in most patients 3.
• High single daily doses of isosorbide dinitrate or isosorbide-5-mononitrate are recommended due to their prolonged duration of action, improved patient compliance, and increased likelihood of maximal anti-ischemic effects 3.

Effective Dosage

• A study comparing 50-mg and 100-mg sustained-release isosorbide mononitrate found that the 100-mg dose provided better improvement in anginal symptoms and quality of life, without producing further adverse effects 5.
• Another study evaluated the efficacy and safety of extended-release isosorbide mononitrate tablets in patients with stable effort angina, and found that doses of 120 and 240 mg administered orally once daily significantly prolonged exercise time to development of moderate effort-induced angina 4 and 12 hours after dosing, without development of nitrate tolerance 6.

Treatment of Angina Pectoris

• Isosorbide mononitrate is used in the treatment of angina pectoris, and its efficacy and safety have been evaluated in several studies 4, 7, 6.
• The primary drugs utilized in the treatment of angina pectoris include organic nitrates, beta-adrenoceptor antagonists, Ca2+ antagonists, and the antithrombotic agents aspirin and heparin 7.