What is Imdur (isosorbide mononitrate) used for?

What is Imdur Used For?

Imdur (isosorbide mononitrate extended-release) is indicated for the prevention of angina pectoris due to coronary artery disease. 1

Primary Indication: Angina Prevention

• Imdur is specifically used to prevent anginal episodes in patients with chronic stable angina, not to abort acute attacks. 1
• The onset of action is not sufficiently rapid to treat an acute anginal episode that is already occurring. 1
• For acute anginal relief, patients need sublingual nitroglycerin or spray formulations. 2

Mechanism of Action

Isosorbide mononitrate works through multiple cardiovascular effects: 3

• Dilates both normal and atherosclerotic epicardial coronary arteries 3
• Promotes dilation of large coronary arteries and enhances collateral flow to ischemic regions 3
• Redistributes coronary blood flow to areas of myocardial ischemia 3
• Reduces myocardial oxygen demand by dilating venous capacitance vessels, decreasing preload 2

Dosing and Efficacy

• The standard starting dose is 60 mg once daily in the morning, providing effective prophylaxis throughout the day for approximately 1 to 12 hours. 4
• Doses can be titrated up to 120-240 mg once daily for patients requiring additional symptom control. 4
• The once-daily formulation using the Durules controlled-release matrix maintains antianginal efficacy without developing classical tolerance. 4, 5

Additional Use: Heart Failure (Specific Populations)

In African American patients with NYHA class III or IV heart failure with reduced ejection fraction, the combination of hydralazine plus isosorbide dinitrate (which includes mononitrate formulations) provides mortality benefit. 2, 3

• This combination should be added to standard heart failure therapy (ACE inhibitors, beta-blockers, and aldosterone antagonists). 2
• The benefit is related to enhanced nitric oxide bioavailability. 3

Critical Contraindications and Precautions

Absolute contraindication: Never use with phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil) due to risk of profound hypotension, myocardial infarction, and death. 2, 3

Additional contraindications and cautions: 2, 3

• Avoid in patients with systolic blood pressure <90 mmHg or >30 mmHg below baseline 2
• Use with extreme caution in aortic stenosis due to risk of marked hypotension 3
• Avoid in marked bradycardia or tachycardia 2

Common Pitfalls

Tolerance management: 4, 5

• The once-daily morning dosing of Imdur provides a built-in "nitrate-free interval" during nighttime hours (at least 10 hours), which prevents tolerance development 3
• This plasma profile is high enough for daytime protection but low enough overnight to avoid tolerance 5

Withdrawal concerns: 6

• Abrupt discontinuation after long-term treatment may exacerbate anginal symptoms 4
• Some patients may experience sudden deterioration requiring hospitalization upon withdrawal 6
• Taper gradually if discontinuation is necessary

Side Effects

• Headache is the most common side effect, usually mild to moderate, typically resolving after 5-6 days of continued use. 4, 7
• Hypotension and dizziness may occur 3
• Headache rarely leads to treatment discontinuation 4

Combination Therapy

Imdur can be effectively combined with beta-blockers for enhanced antianginal protection superior to beta-blocker monotherapy. 8

• The combination significantly increases total exercise capacity and time to onset of chest pain 8
• Reduces anginal attack rate and nitroglycerin consumption 8