Is Imdur (isosorbide mononitrate) safe to use in patients with pulmonary hypertension?

Imdur (Isosorbide Mononitrate) Should Be Avoided in Patients with Pulmonary Hypertension

Imdur (isosorbide mononitrate) is not recommended for patients with pulmonary hypertension due to potential risks of severe hypotension and worsening of right ventricular function.

Rationale for Avoiding Imdur in Pulmonary Hypertension

Mechanism of Concern

• Nitrates like Imdur cause systemic vasodilation which can lead to:
  • Decreased systemic vascular resistance (SVR)
  • Potential reversal of the SVR/PVR (pulmonary vascular resistance) ratio
  • Risk of right ventricular ischemia if systolic pulmonary arterial pressure exceeds systolic systemic arterial pressure 1

FDA Warning

• The FDA label for isosorbide mononitrate specifically warns about:
  • Potential severe hypotension when combined with other vasodilators
  • Difficulty in rapidly terminating the effects of the drug if adverse events occur
  • Need for careful hemodynamic monitoring if used in conditions with compromised cardiac function 2

Guideline Recommendations for Pulmonary Hypertension

Treatment Principles

• European Society of Cardiology (ESC) and European Respiratory Society (ERS) guidelines emphasize:
  • Maintaining systemic vascular resistance greater than pulmonary vascular resistance is a major treatment principle 1
  • Conventional vasodilators like calcium channel blockers are not recommended in pulmonary hypertension associated with lung diseases 1

Approved Therapies

• For pulmonary arterial hypertension (PAH), only specific classes of medications are recommended:

  • Phosphodiesterase-5 inhibitors (e.g., sildenafil)
  • Endothelin receptor antagonists
  • Soluble guanylate cyclase stimulators
  • Prostanoids 3

• The American Thoracic Society explicitly recommends against using advanced vasoactive agents for pulmonary hypertension resulting from left heart disease or hypoxemic lung diseases (Group II or III PH) 1

Alternative Approaches for Pulmonary Hypertension

Preferred Medications

• For PAH patients who demonstrate vasoreactivity:

  • High-dose calcium channel blockers (nifedipine, diltiazem, amlodipine) may be used under careful monitoring 1

• For other PAH patients:

  • Sildenafil has demonstrated effectiveness as a pulmonary vasodilator with the added benefit of increasing cardiac output 4
  • Specialized PAH centers should guide therapy decisions based on risk stratification 3

Supportive Care

• All pulmonary hypertension patients should receive:
  • Oxygen therapy if hypoxemic (arterial blood O₂ pressure <8 kPa/60 mmHg)
  • Diuretics for signs of right ventricular failure and fluid retention
  • Consideration for referral to specialized pulmonary hypertension centers 1, 3

Conclusion

Imdur and other nitrates should be avoided in patients with pulmonary hypertension due to their potential to cause systemic vasodilation that may worsen the hemodynamic balance between systemic and pulmonary circulation. This could lead to right ventricular ischemia and clinical deterioration. Instead, patients should be managed with approved pulmonary hypertension-specific therapies under the guidance of specialists at centers experienced in treating this condition.