What is the recommended treatment for erectile dysfunction using Viagra (sildenafil)?

Sildenafil (Viagra) for Erectile Dysfunction

First-Line Treatment Recommendation

Initiate sildenafil as first-line therapy for erectile dysfunction at a starting dose of 50 mg taken approximately 1 hour before sexual activity, with dose adjustment to 25-100 mg based on efficacy and tolerability, taken no more than once daily. 1, 2

Dosing Strategy

Starting Dose and Titration

• Begin with 50 mg taken 1 hour before sexual activity as the standard starting dose 1, 3
• Adjust to 100 mg if 50 mg provides insufficient response, or reduce to 25 mg if side effects are problematic 1, 3
• Maximum frequency is once daily 2
• Sildenafil shows dose-related improvement from 25 mg to 50 mg, but less additional benefit when increasing from 50 mg to 100 mg 2, 4

Alternative Approach: Starting at 100 mg

• Starting directly at 100 mg is safe and may reduce anxiety about sexual performance—56% of men felt no anxiety about the next intercourse attempt with 100 mg vs 39% with 50 mg 5
• The 100 mg starting dose improves treatment satisfaction and sexual experience compared to 50 mg, with no increase in adverse events 5

Adequate Trial Before Declaring Failure

• Ensure 4-8 attempts at proper dosing before declaring treatment failure 2
• Before switching therapies, verify: adequate sexual stimulation, proper timing (1 hour before activity), absence of excessive alcohol, no interfering medications, and relationship factors 4, 6

Efficacy Across Populations

General Population

• 69% success rate for sexual intercourse with sildenafil vs 35.5% with placebo 2
• 73-88% of patients report improved erections vs 26-32% with placebo 2, 4

Special Populations

• Diabetes: 56% of men with diabetes reported improved erections vs 10% with placebo, though response is less robust than in the general population 2, 7
• Cardiovascular disease/hypertension: 71% response rate vs 27% with placebo 8
• Depression: 78% response rate vs 29% with placebo 8
• Post-prostatectomy: Effective but with diminished response compared to general ED population 2
• Age: Efficacy is maintained regardless of age (<45,46-64, ≥65 years), though older patients may require lower starting doses (25 mg) 3, 8

Critical Safety Considerations

Absolute Contraindications

• Never prescribe sildenafil with nitrates—this combination causes potentially fatal hypotension 1, 2, 9
• Nitrates include: nitroglycerin (any form), isosorbide mononitrate/dinitrate, and "poppers" (amyl nitrate/nitrite) 9
• If emergency nitrate administration is required, wait at least 24 hours after sildenafil use before giving nitrates 2, 6

Cardiovascular Risk Assessment

• Most ED patients fall into low-risk category and can safely receive sildenafil, including those with: asymptomatic CAD with <3 risk factors, controlled hypertension, mild stable angina, successful coronary revascularization, uncomplicated past MI, mild valvular disease, and CHF (NYHA class I) 6
• Refer to cardiology before prescribing if cardiovascular risk is indeterminate or patient cannot perform moderate physical activity 6

Dose Adjustments for Special Circumstances

• Reduce to 25 mg in elderly patients, those with hepatic or renal impairment, or those receiving CYP3A4 inhibitors (ritonavir, ketoconazole, erythromycin, cimetidine) 3
• Severe hepatic impairment: PDE5 inhibitors generally not recommended 6

Adverse Effects Profile

Common Side Effects (Mild to Moderate)

• Headache (11%), flushing, dyspepsia (9%), nasal congestion (6%), visual disturbances, myalgia, dizziness 1, 4, 3, 7
• Serious adverse events occur in <2% of patients, with no significant difference compared to placebo 4

Rare but Serious Events

• Sudden vision loss (NAION): Advise patients to seek immediate medical attention for sudden loss of vision in one or both eyes 9
• Sudden hearing loss: May be accompanied by tinnitus and dizziness; requires prompt medical attention 9
• Cardiovascular events in postmarketing surveillance generally occurred in patients with other known risk factors 3

Mechanism and Patient Education

How Sildenafil Works

• Selectively inhibits phosphodiesterase type 5 (PDE5), allowing corpus cavernosum smooth muscle to relax and potentiating erections during sexual stimulation 3
• Sexual stimulation is necessary for the medication to work—sildenafil does not cause automatic erections 4, 6

Pharmacokinetics

• Rapidly absorbed with peak plasma concentrations within 1 hour 3
• Elimination half-life is 3-5 hours 3
• Food may delay absorption, so taking on an empty stomach may improve onset 3

Comparison with Other PDE5 Inhibitors

Sildenafil vs Tadalafil

• Both are equally effective first-line treatments (69% success rate for both) 2
• Primary difference: tadalafil has longer duration of action (up to 36 hours vs 4-5 hours for sildenafil) 2
• Choose based on patient preference: sildenafil for planned sexual activity, tadalafil for spontaneity or daily dosing option 1, 2
• Cost, ease of use, and adverse effects profile should guide selection when efficacy is equivalent 1

Combination Therapy Considerations

Testosterone Deficiency

• For men with ED and testosterone deficiency, combining sildenafil with testosterone therapy may be more effective than sildenafil alone 6
• Testosterone therapy alone is not effective monotherapy for ED 6
• Check total testosterone, free testosterone, and SHBG if response to sildenafil is suboptimal 6

Benign Prostatic Hyperplasia (BPH)

• If treating both ED and BPH, consider switching to tadalafil 5 mg daily, which treats both conditions simultaneously (FDA-approved indication) 6
• Avoid combining sildenafil with alpha-blockers for BPH, as this offers no advantage and increases hypotension risk 6

Ongoing Management

Follow-Up Assessment

• Periodically assess efficacy, side effects, and changes in health status or medications 4, 6
• Verify cardiovascular health hasn't changed 6
• Review new medications for potential interactions 6
• Confirm proper use: timing, sexual stimulation, alcohol consumption, relationship factors 4, 6

When to Switch Therapies

• If inadequate response after 4-8 attempts at maximum dose, consider switching to a different PDE5 inhibitor (vardenafil or tadalafil) 2, 6
• Address modifiable factors before switching: hormonal abnormalities, drug interactions, timing issues, inadequate sexual stimulation, excessive alcohol, relationship problems 4, 6