Is it safe to prescribe erectile dysfunction (ED) medication, such as sildenafil (Viagra) or tadalafil (Cialis), to a male patient with congestive heart failure (CHF)?

Erectile Dysfunction Medications Are Safe in Stable Heart Failure, But Contraindicated with Nitrates

Phosphodiesterase-5 (PDE5) inhibitors such as sildenafil, tadalafil, and vardenafil are safe and effective first-line treatments for erectile dysfunction in men with congestive heart failure, provided they are not taking nitrates and their heart failure is compensated. 1, 2

Risk Stratification Required Before Prescribing

Before prescribing any ED medication to a patient with CHF, you must classify their cardiovascular risk using the Princeton Consensus Panel criteria 1, 2:

Low-Risk Patients (Safe to Prescribe PDE5 Inhibitors)

• NYHA Class I heart failure (mild symptoms, no limitation of physical activity) 1, 2
• Controlled hypertension 1
• Mild, stable angina 1
• Successful coronary revascularization 1
• Uncomplicated past myocardial infarction 1
• Asymptomatic coronary artery disease with <3 cardiac risk factors 1

High-Risk Patients (Do NOT Prescribe Until Stabilized)

• NYHA Class II or greater heart failure within the last 6 months 3
• NYHA Class III-IV heart failure (moderate to severe symptoms) 1, 2
• Unstable or refractory angina 1
• Uncontrolled hypertension 1
• Myocardial infarction within the last 90 days 3
• Uncontrolled arrhythmias 3
• Hypotension (<90/50 mmHg) 3
• Stroke within the last 6 months 3

Intermediate-Risk Patients

• Refer to cardiology for exercise stress testing before prescribing 2
• If patient can achieve ≥5-6 METs on exercise testing without symptoms, they can safely use PDE5 inhibitors 2, 4

Absolute Contraindication: Nitrate Use

PDE5 inhibitors are absolutely contraindicated in any patient taking nitrates in any form due to the risk of severe, potentially life-threatening hypotension. 1, 5, 3, 6, 4

• This includes long-acting nitrates, sublingual nitroglycerin, nitrate patches, and nitric oxide donors 1, 4
• If a patient on sildenafil develops chest pain requiring nitrates, at least 24 hours must elapse after the last sildenafil dose before nitrate administration 5, 4
• For tadalafil, at least 48 hours must elapse due to its longer half-life 3
• Even in life-threatening situations, nitrates should only be given under close medical supervision with hemodynamic monitoring after these time intervals 3

Evidence Supporting Safety and Efficacy in CHF

Short-term studies demonstrate that PDE5 inhibitors have favorable hemodynamic effects in patients with heart failure and reduced ejection fraction (HF-REF). 1

• In a randomized controlled trial of 23 men with CHF, sildenafil 50mg reduced heart rate and blood pressure at rest and during exercise, improved peak oxygen consumption from 16.6 to 17.7 mL/kg/min, and increased exercise time from 12.3 to 13.7 minutes 7
• A double-blind, placebo-controlled study of 132 men with stable CHF showed 74% of sildenafil-treated patients reported improved erections versus 18% on placebo, with only transient side effects (headache, flushing) 8
• In 35 patients with NYHA Class II-III CHF, sildenafil improved erectile function scores, reduced depression symptoms, and enhanced quality of life without symptomatic hypotension 9
• A retrospective analysis of 357 patients with ischemic heart disease (not on nitrates) showed 70% improvement in erections with sildenafil versus 20% with placebo, with cardiovascular adverse event rates similar to patients without heart disease 6

Special Considerations and Cautions

Hypertrophic Cardiomyopathy Warning

• PDE5 inhibitors may worsen left ventricular outflow tract obstruction in patients with hypertrophic cardiomyopathy, which can be a concern in some HF-PEF patients 1
• Use with caution and awareness of this potential complication 1

Sexual Activity Risk Assessment

• Sexual activity increases physical exertion to 3-4 METs, which is generally safe for stable CHF patients 1, 2, 4
• The absolute risk of myocardial infarction during sexual activity is extremely low (20 chances per million per hour even in post-MI patients) 1
• Advise patients to be well-rested before sexual activity and to stop if they become short of breath 2

Hemodynamic Effects

• PDE5 inhibitors cause mild systemic vasodilation with transient decreases in blood pressure 3
• Tadalafil 20mg causes a mean maximal decrease of 1.6/0.8 mmHg in healthy subjects 3
• Patients with severely impaired autonomic control of blood pressure may be particularly sensitive 3

Drug Interactions

• Potent CYP3A4 inhibitors (erythromycin, cimetidine, some statins) increase sildenafil plasma levels 4
• Creatinine clearance <30 mL/min increases sildenafil levels 4
• Alpha-blockers and antihypertensives may have additive blood pressure-lowering effects 3

Practical Prescribing Algorithm

1. Confirm heart failure is stable (NYHA Class I or compensated Class II) 1, 2
2. Verify patient is NOT taking nitrates 1, 5, 3
3. Screen for hypertrophic cardiomyopathy if HF-PEF 1
4. Start with lowest effective dose (sildenafil 25-50mg, tadalafil 5-10mg) 1
5. Titrate based on response and tolerability 5
6. Counsel patient to report chest pain, dyspnea, or dizziness during sexual activity 2
7. Advise patient never to take nitrates within 24 hours of sildenafil or 48 hours of tadalafil 5, 3

Alternative Approaches for Higher-Risk Patients

For patients with decompensated or advanced heart failure who cannot safely engage in sexual intercourse, encourage less energy-demanding activities such as hugging, kissing, and fondling 2. Regular exercise programs, when medically appropriate, can improve exercise capacity and potentially make sexual activity safer over time 2.