What medications are contraindicated with Viagra (sildenafil)?

Medications Contraindicated with Viagra (Sildenafil)

Nitrates in any form are absolutely contraindicated with Viagra due to the risk of severe, potentially fatal hypotension. 1

Contraindicated Medications

Absolute Contraindications:

• Organic Nitrates (in any form, regular or intermittent use):
  • Nitroglycerin (sublingual, spray, transdermal, intravenous)
  • Isosorbide dinitrate
  • Isosorbide mononitrate
  • Pentaerythritol tetranitrate
  • Erythritol tetranitrate
  • Nicorandil

The combination of PDE5 inhibitors like Viagra with nitrates causes synergistic vasodilation, resulting in profound and potentially life-threatening hypotension that can lead to myocardial infarction and death 2.

Time Restrictions After Viagra Use:

• Wait at least 24 hours after taking sildenafil (Viagra) before using any nitrate medication 2, 3
• Wait at least 48 hours after taking tadalafil (Cialis) before using any nitrate medication 2, 3
• For vardenafil (Levitra), a specific time interval hasn't been definitively established, but 24 hours is generally recommended 2

Medications Requiring Caution

Alpha-Blockers:

• Doxazosin, tamsulosin, alfuzosin, etc.
• May cause additive blood pressure-lowering effects
• Risk of orthostatic hypotension, especially when starting therapy 4

Strong CYP3A4 Inhibitors (may increase sildenafil levels):

• Ritonavir and other HIV protease inhibitors
• Ketoconazole, itraconazole
• Erythromycin
• Clarithromycin
• Cimetidine 5

Lower starting doses of sildenafil (25mg) are recommended when used with these medications.

Other Medications Requiring Dose Adjustments:

• Cyclosporine
• Rifampin and other CYP3A4 inducers (may decrease sildenafil levels)
• Multiple antihypertensive medications (potential for additive blood pressure reduction) 6

Special Considerations

Cardiovascular Risk Assessment:

• Patients with unstable angina should not use Viagra 7
• Caution is advised within 6 months of acute myocardial infarction or stroke 7
• Patients with uncontrolled hypertension or severe cardiac failure should use with caution 7

Monitoring Recommendations:

• Patients on continuing PDE5 inhibitor therapy should have periodic follow-up to assess:
  • Efficacy
  • Side effects
  • Any significant changes in health status or medications 2

Common Pitfalls to Avoid

1. Emergency situations: In a cardiac emergency requiring nitrates, inform medical personnel about recent Viagra use
2. Self-medication: Patients should never combine Viagra with over-the-counter nitrate medications
3. Medication changes: Always inform healthcare providers about Viagra use before starting new medications
4. Alcohol consumption: Excessive alcohol may increase the risk of hypotension when combined with Viagra

While most antihypertensive medications (beta-blockers, diuretics, ACE inhibitors, calcium channel blockers) can be used with sildenafil, they may cause additive but not potentiating blood pressure decreases 6. The combination is generally safe but requires monitoring, especially when initiating therapy.