What are the efficacy and safety of long-term use of Cialis (tadalafil) 5 mg daily and Viagra (sildenafil) 50 mg as needed in adult males with erectile dysfunction, particularly those with cardiovascular risk factors?

Long-Term Efficacy and Safety of Cialis 5 mg Daily vs. Viagra 50 mg As-Needed

For long-term erectile dysfunction treatment, both Cialis (tadalafil) 5 mg daily and Viagra (sildenafil) 50 mg as-needed demonstrate equivalent efficacy (approximately 69% success rates vs. 33% placebo), with the choice primarily determined by patient preference for spontaneous vs. planned sexual activity and individual tolerability profiles. 1, 2

Comparative Efficacy

Success Rates and Clinical Outcomes

• Both medications achieve similar overall success rates: tadalafil demonstrates 69% successful intercourse attempts (range 50-85%) compared to placebo 33%, while sildenafil achieves 69% success (range 52-85%) versus placebo 35.5% 2
• Both agents improve erections in 73-88% of patients compared to 26-32% with placebo 2, 3
• Tadalafil does NOT show dose-dependent improvement between 5 mg, 10 mg, and 20 mg doses, meaning efficacy remains consistent across this dosing range 2
• Sildenafil demonstrates a dose-response relationship, with 50 mg being more effective than 25 mg, though 100 mg shows minimal additional benefit over 50 mg 2, 3

Duration of Action and Timing Considerations

• Tadalafil 5 mg daily eliminates the need to time medication with sexual activity entirely, providing continuous readiness for up to 36 hours after each dose 1, 2
• Sildenafil 50 mg requires timing approximately 1 hour before sexual activity with a duration of action of 4-5 hours 1, 4
• FDA data confirms that tadalafil maintains efficacy at 24 hours (61% success) and 36 hours (64% success) post-dosing compared to placebo (37% at both timepoints) 5

Long-Term Efficacy Data

• Tadalafil once-daily demonstrated sustained efficacy in studies up to 24 weeks duration without diminution of treatment effect over time 5
• In the 6-month double-blind study, the treatment effect of tadalafil did not diminish over time 5
• Sildenafil maintained efficacy in long-term studies up to 1 year 4

Safety and Tolerability Profiles

Common Adverse Events

• Tadalafil 5 mg daily has lower rates of flushing compared to other PDE5 inhibitors, with common side effects including dyspepsia, headache, back pain, nasal congestion, and myalgia 2
• Sildenafil 50 mg commonly causes headache, flushing, dyspepsia, nasal congestion, and abnormal vision 3, 4
• All adverse events occur in a dose-dependent fashion, with serious adverse events occurring in less than 2% of patients for both medications 1, 3

Critical Safety Contraindications

• Both medications are absolutely contraindicated with concurrent nitrate therapy due to potentially fatal hypotension risk 1, 2
• Required nitrate washout periods: minimum 24 hours for sildenafil and 24-48 hours for tadalafil before emergency nitrate administration 1, 3
• Use caution with lower initial doses in mild-to-moderate hepatic or renal impairment; generally avoid in severe renal or liver disease 1, 2

Cardiovascular Risk Stratification

• The majority of ED patients fall into the low-risk category and can safely receive PDE5 inhibitors, including those with asymptomatic coronary artery disease with <3 risk factors, controlled hypertension, mild stable angina, successful coronary revascularization, uncomplicated past MI, mild valvular disease, and CHF (NYHA class I) 2
• Patients whose cardiovascular risk is indeterminate or who cannot perform moderate physical activity (walk 1 mile in 20 minutes or climb 2 flights of stairs in 20 seconds) should be referred to cardiology before prescribing 2
• High-risk patients should defer treatment, including those with unstable angina, uncontrolled hypertension, recent MI, NYHA Class II-IV heart failure, or severe valvular disease 2

Special Population Considerations

Diabetes and Comorbidities

• Both medications remain effective in diabetic patients, though with less robust response compared to the general population 1, 2
• Efficacy is independent of diabetes duration, glycemic control, or microvascular complications 1
• Both agents are effective in patients with cardiovascular disease, post-prostatectomy, depression, and other comorbidities 2, 3

Testosterone Deficiency

• For men with ED and testosterone deficiency, combining either medication with testosterone therapy may be more effective than PDE5 inhibitor monotherapy 1, 2
• Testosterone therapy alone is not an effective monotherapy for ED 2

Optimizing Treatment Success

Defining an Adequate Trial

• An adequate trial requires at least 5 separate attempts at maximum tolerated dose before declaring treatment failure 2
• Many apparent failures result from inadequate trials, improper timing, lack of sexual stimulation, or modifiable factors 2
• Sexual stimulation is necessary for both medications to be effective, and incorrect use accounts for a large percentage of treatment failures 1, 2

Modifiable Factors to Address Before Switching

• Evaluate hormonal abnormalities, food or drug interactions, timing and frequency of dosing, adequacy of sexual stimulation, heavy alcohol use, and relationship issues with partner 2, 3
• Heavy alcohol use should be avoided as it may impair erectile function and increase risk of adverse effects 2

Clinical Decision Algorithm

Choose Tadalafil 5 mg Daily When:

• Patient prefers spontaneous sexual activity without timing medication 1, 2
• Patient has concurrent benign prostatic hyperplasia (FDA-approved for dual indication) 2, 5
• Patient desires continuous readiness over multiple days 2
• Patient experienced significant flushing with sildenafil 2

Choose Sildenafil 50 mg As-Needed When:

• Patient prefers planned sexual activity with predictable timing 1, 2
• Sexual activity occurs infrequently (less than 2-3 times weekly) 1
• Patient prioritizes highest single-dose efficacy (dose-response relationship exists) 2, 3
• Cost considerations favor as-needed dosing 6

Switching Between Agents

• If partial response to sildenafil 50 mg as-needed, consider switching to tadalafil 5 mg daily, which has demonstrated ability to restore normal erectile function (IIEF-EF ≥26) in 39-40% of men with incomplete response to PRN PDE5 inhibitors 7, 8
• Titrate doses to find optimal balance between efficacy and side effects 2

Ongoing Management Requirements

• Periodic follow-up should assess efficacy, side effects, and any significant changes in health status or medications 2, 3
• Verify that cardiovascular health hasn't changed, review new medications, assess treatment effectiveness, and evaluate side effects 2
• ED diagnosis provides an opportunity to evaluate cardiovascular risk factors, as ED shares common risk pathways with cardiovascular disease 1