What is the recommended dosing for Viagra (sildenafil) in the treatment of erectile dysfunction?

Sildenafil (Viagra) Dosing for Erectile Dysfunction

The recommended dosing for sildenafil (Viagra) in the treatment of erectile dysfunction is 25-100mg taken as needed approximately 1 hour before sexual activity, with a starting dose of 50mg for most patients and dose adjustments based on efficacy and tolerability. 1

Initial Dosing and Adjustments

• Standard starting dose: 50mg as needed, taken approximately 1 hour before sexual activity 1, 2
• Maximum dose: 100mg once daily 1, 2
• Lower starting dose (25mg) recommended for:
  • Elderly patients (≥65 years) 2
  • Patients with hepatic or renal impairment 2
  • Patients taking CYP3A4 inhibitors (e.g., ritonavir, saquinavir, ketoconazole, erythromycin, cimetidine) 2

Dose Optimization

• Allow at least 5 separate occasions at the maximum dose before declaring treatment ineffective 1
• Consider dose escalation to 100mg if 50mg is insufficient but well-tolerated 3
• Research shows the 100mg dose may provide:
  • Reduced anxiety about the next intercourse attempt (56% vs 39% with 50mg) 3
  • Improved treatment satisfaction compared to 50mg 3
  • No significant increase in adverse events compared to 50mg 3, 4

Administration Guidelines

• Take no more than once daily 2
• Take approximately 1 hour before anticipated sexual activity 2, 5
• Efficacy may be delayed if taken with a high-fat meal
• Sildenafil requires sexual stimulation to be effective 2

Special Populations

• Diabetes: Effective and well-tolerated in men with diabetes, with 56% reporting improved erections compared to 10% with placebo 5
• Spinal cord injury: Effective in men with erectile dysfunction due to spinal cord injury (T6-L5), with 75% reporting improved erections 6
• Elderly patients: Remains effective across age groups, though response rates may decrease with age:
  • <65 years: 80% reporting improved erections
  • 65-74 years: 69% reporting improved erections
  • ≥75 years: 59% reporting improved erections 4

Cardiovascular Considerations and Contraindications

• Absolute contraindication: Concurrent use of nitrates due to risk of severe hypotension 1
• Wait at least 24 hours after sildenafil before administering nitrates 1
• Exercise caution with alpha-blockers 1
• Assess cardiovascular risk before initiating treatment:
  • Sexual activity is equivalent to walking 1 mile in 20 minutes or climbing 2 flights of stairs in 20 seconds
  • Patients unable to perform this level of activity without symptoms should be referred to a cardiologist before treatment 1

Common Side Effects

• Headache (most common) 2, 5, 4
• Flushing 2, 4
• Dyspepsia 2, 5
• Nasal congestion 2, 5
• Abnormal vision (transient) 2

Clinical Pearls

• Most side effects are transient and mild to moderate in severity 2
• Efficacy is maintained in long-term (1-year) studies 2
• Treatment failure should only be declared after at least 5 attempts at the maximum tolerated dose 1
• Consider reassessing treatment response after 4-6 weeks 1
• Higher doses (100mg) may be particularly beneficial for reducing anxiety about sexual performance 3