Sildenafil for Erectile Dysfunction: Treatment Protocol
First-Line Recommendation
Oral sildenafil should be offered as first-line therapy for erectile dysfunction unless contraindicated, starting at 50 mg taken as needed approximately 1 hour before sexual activity, with a maximum frequency of once daily. 1, 2
Cardiovascular Risk Stratification (Mandatory Before Treatment)
Before prescribing sildenafil, assign patients to cardiovascular risk categories using the Princeton Consensus Panel criteria: 1, 2
High-Risk Patients (Defer Treatment Until Cardiac Stabilization):
- Unstable or refractory angina
- Uncontrolled hypertension
- Left ventricular dysfunction/CHF (NYHA class II or greater)
- MI or stroke within previous 2 weeks
- High-risk arrhythmias
- Hypertrophic obstructive cardiomyopathies
- Moderate-to-severe valvular disease 1, 2
Low-Risk Patients (May Proceed with Treatment):
- Asymptomatic coronary artery disease with <3 risk factors
- Controlled hypertension
- Mild, stable angina
- Successful coronary revascularization
- Uncomplicated past MI
- Mild valvular disease
- CHF (NYHA class I) 1
Indeterminate-Risk Patients: Refer to cardiology before initiating ED therapy. 1
Dosing Protocol
Starting Dose: Begin with sildenafil 50 mg taken as needed, approximately 1 hour before sexual activity, maximum once daily. 3, 4
Dose Titration:
- If 50 mg is inadequate, increase to 100 mg (maximum dose). 3, 4
- For elderly patients, those with hepatic/renal impairment, or those taking CYP3A4 inhibitors (ritonavir, saquinavir, ketoconazole, erythromycin, cimetidine), reduce starting dose to 25 mg. 3
- Higher doses (100 mg) provide greater efficacy with improved treatment satisfaction and reduced anxiety about sexual performance compared to 50 mg, without increased adverse events. 4
Adequate Trial Definition: Require at least 5 separate occasions at the maximum tolerated dose before declaring treatment failure. 2
Critical Contraindications
Absolute Contraindication: Never prescribe sildenafil to patients taking nitrates—this combination causes potentially fatal hypotension. 1, 2, 5, 6
Nitrate Washout Periods (Emergency Situations Only):
- Wait at least 24 hours after sildenafil before administering nitrates under close medical supervision. 1, 5
- For tadalafil (if patient switches), wait 48 hours. 1, 5
Patient Counseling (Essential for Success)
Provide explicit instructions to prevent treatment failure: 2, 7
- Sexual stimulation is required—the medication does not work without arousal. 7
- Timing flexibility: While traditionally recommended 1 hour before intercourse, sildenafil maintains efficacy when taken 30-60 minutes before or even during meals, with duration of action exceeding 10 hours. 8
- Food effects: No significant loss of efficacy occurs when taken with meals, contrary to older recommendations. 8
- Avoid excessive alcohol: Heavy drinking impairs response. 2, 7
Expected Efficacy
Sildenafil demonstrates 73-88% improvement in erectile function compared to 26-32% with placebo. 7 Success rates reach 69% versus 35% with placebo in clinical trials. 2 Most patients find 50-100 mg doses effective. 3
Common Adverse Effects
Expect transient, mild-to-moderate side effects: 2, 5, 7, 3
- Headache
- Flushing
- Nasal congestion
- Dyspepsia
- Visual disturbances
- Back pain and myalgia
Serious adverse events occur in <2% of patients, with no significant difference from placebo. 5, 7
Troubleshooting Treatment Failures
Before switching therapies, evaluate modifiable factors: 2, 7
- Inadequate sexual stimulation
- Incorrect timing or frequency of dosing
- Hormonal abnormalities (measure free testosterone if non-responsive, especially with decreased libido, fatigue, or testicular atrophy) 2, 7
- Food or drug interactions
- Relationship issues with partner
- Heavy alcohol use 2, 7
After re-education on proper use and dose optimization, many initial non-responders become responders. 5
Lifestyle Modifications (Concurrent with Pharmacotherapy)
Counsel all ED patients on risk factor modification: 2, 5
- Smoking cessation
- Weight loss if overweight
- Increased physical activity
- Reduced alcohol consumption
- Optimal management of diabetes, hypertension, and dyslipidemia 2, 5
Follow-Up Monitoring
Periodically assess efficacy, side effects, and changes in health status or medications. 5, 7 Ensure patients understand that response may improve over multiple attempts.
Second-Line Options (If Sildenafil Fails After Adequate Trial)
Proceed to intraurethral alprostadil suppositories, intracavernous vasoactive drug injection, or vacuum constriction devices. 2 Consider testosterone replacement if morning total testosterone <300 ng/dL, as combination therapy may be more effective than PDE5 inhibitors alone. 5