How to manage erectile dysfunction (ED) in a patient taking Imdur (isosorbide mononitrate) for angina?

Management of Erectile Dysfunction in Patients Taking Imdur

Phosphodiesterase type 5 (PDE5) inhibitors are absolutely contraindicated in patients taking Imdur (isosorbide mononitrate) due to the risk of severe, potentially life-threatening hypotension. 1

Understanding the Contraindication

The combination of nitrates (like Imdur) and PDE5 inhibitors creates a dangerous drug interaction:

• PDE5 inhibitors should not be used concomitantly with nitrate medications due to risk for severe hypotension 1
• Nitrates should not be administered to patients who have received PDE5 inhibitors within specific timeframes:
  • 24 hours of sildenafil or vardenafil use
  • 48 hours of tadalafil use 1

Research confirms this interaction is significant - coadministration of sildenafil with isosorbide mononitrate produced significantly greater reductions in blood pressure than isosorbide mononitrate alone 2.

Treatment Algorithm for ED in Patients on Imdur

Step 1: Evaluate Necessity of Nitrate Therapy

• Consult with the patient's cardiologist to determine if:
  • Nitrate therapy can be safely discontinued
  • Alternative anti-anginal medications without PDE5 inhibitor interactions can be substituted 3

Step 2: If Nitrates Cannot Be Discontinued

Choose from these non-PDE5 inhibitor options:

1. Vacuum Erection Devices (VEDs)

   • Non-pharmacological option with 90% initial efficacy
   • Good option for older patients with infrequent sexual activity
   • Contraindicated in patients with bleeding disorders 3

2. Intracavernosal Injection Therapy

   • Most effective non-surgical treatment for ED 1
   • Options include:
     • Alprostadil (PGE1) monotherapy
     • Combination therapy (bimix or trimix)
   • Initial trial dose should be administered under healthcare provider supervision 1

3. Intraurethral Alprostadil Suppositories

   • Less invasive than injection therapy
   • Initial dose should be administered under healthcare provider supervision due to risk of syncope (3% of patients) 1

4. Penile Prostheses

   • Reserved for patients who have failed or cannot use less invasive treatments
   • High satisfaction rates but irreversible 3

Step 3: If Nitrates Can Be Discontinued

If the cardiologist determines nitrates can be safely discontinued:

1. Wait appropriate time after last nitrate dose (based on half-life of isosorbide mononitrate)
2. Begin PDE5 inhibitor therapy:
   • Sildenafil (25-100mg as needed)
   • Tadalafil (5-20mg as needed, or 2.5-5mg daily)
   • Vardenafil (5-20mg as needed)
   • Avanafil (50-200mg as needed) 3

Important Considerations and Cautions

• Cardiovascular Risk Assessment: Ensure patient has sufficient cardiac health for sexual activity before initiating any ED treatment 3

• Hemodynamic Effects: Research shows isosorbide mononitrate reduces mean arterial pressure more significantly than PDE5 inhibitors alone (-22 vs -10 mmHg), highlighting the danger of combining these medications 4

• Alternative Anti-Anginal Medications: If appropriate, consider switching to other anti-anginal medications that don't interact with PDE5 inhibitors, such as beta-blockers or calcium channel blockers 3, 5

• Monitoring: If transitioning from nitrates to alternative anti-anginal therapy, close monitoring of angina symptoms is essential 5

Common Pitfalls to Avoid

1. Never prescribe PDE5 inhibitors to patients currently taking nitrates - this is an absolute contraindication that can lead to severe hypotension 1

2. Don't assume all ED treatments are contraindicated - non-PDE5 inhibitor options can be safely used with nitrates 1

3. Avoid abrupt discontinuation of nitrates without cardiologist consultation - this could precipitate angina symptoms 6

4. Don't overlook the importance of patient education about the serious risks of combining nitrates with PDE5 inhibitors obtained from any source 3