Imdur (Isosorbide Mononitrate) Use in CHF vs HTN
Imdur is used for congestive heart failure in specific populations, not for hypertension. 1, 2
Primary Indication: Heart Failure (Not Hypertension)
Nitrates, including isosorbide mononitrate (Imdur), have not been shown to be useful in the management of hypertension. 1 The FDA label explicitly states that the benefits of isosorbide mononitrate in patients with congestive heart failure have not been established, and careful clinical or hemodynamic monitoring must be used to avoid the hazards of hypotension and tachycardia if used in this setting. 3
Specific CHF Applications
When to Use in Heart Failure:
Hydralazine plus isosorbide dinitrate (or mononitrate) should be added to standard therapy (diuretic, ACE inhibitor/ARB, and β-blocker) in African American patients with NYHA class III or IV heart failure with reduced ejection fraction (Class I recommendation, Level of Evidence A). 1
This combination may be used in patients who are intolerant to ACE inhibitors or ARBs (though this is a secondary option). 1, 2
The combination works through complementary mechanisms: hydralazine causes arterial vasodilation while isosorbide provides venous vasodilation, reducing both preload and afterload. 4, 2
Evidence Base:
The combination of hydralazine-isosorbide dinitrate reduced mortality by approximately 40% in African American patients with advanced heart failure when added to standard therapy. 1, 2
Isosorbide mononitrate produces hemodynamic improvements in CHF patients already on ACE inhibitors, with persistent reductions in pulmonary capillary wedge pressure and pulmonary artery pressure. 5, 6
Why NOT for Hypertension:
Nitrates are not antihypertensive agents - they cause tolerance with continuous use and are ineffective for sustained blood pressure control. 1, 7
Long-acting nitrates are indicated for angina treatment, not hypertension management. 1
The vasodilatory effects can cause problematic hypotension rather than controlled BP reduction. 3
Critical Contraindications and Precautions:
Absolutely contraindicated with phosphodiesterase inhibitors (sildenafil, tadalafil) due to risk of severe hypotension, MI, and death. 2, 3
Avoid in severe hypotension (systolic BP <90 mmHg). 2
Use with extreme caution in aortic stenosis due to risk of marked hypotension. 2
Tolerance Prevention Strategy:
A nitrate-free interval of at least 10 hours is required to prevent tolerance development. 8, 7
Once-daily dosing of sustained-release formulations (like Imdur 60mg) provides daytime anti-anginal protection while allowing overnight nitrate-free intervals. 7, 9, 10
Combining nitrates with ACE inhibitors or hydralazine may help prevent tolerance. 8