What is the recommended dosage of tadalafil (phosphodiesterase type 5 (PDE5) inhibitor) for erectile dysfunction (ED)?

Tadalafil Dosing for Erectile Dysfunction

For erectile dysfunction, tadalafil is recommended at a starting dose of 10 mg as needed prior to sexual activity, which may be increased to 20 mg or decreased to 5 mg based on individual efficacy and tolerability; alternatively, daily dosing can begin at 2.5 mg with possible increase to 5 mg daily. 1

As-Needed Dosing Regimen

• Starting dose: 10 mg taken prior to anticipated sexual activity 1
• Dose adjustment: May be increased to 20 mg or decreased to 5 mg based on response and side effects 1
• Maximum frequency: Once per day for most patients 1
• Timing considerations: Can improve erectile function for up to 36 hours following dosing 1, 2
• Onset of action: Significant erectogenic effect can occur as early as 16 minutes after taking 20 mg dose 3

Once-Daily Dosing Regimen

• Starting dose: 2.5 mg taken at approximately the same time every day 1
• Dose adjustment: May be increased to 5 mg based on efficacy and tolerability 1
• Advantage: Eliminates need to time medication with sexual activity 4, 5
• Efficacy: Daily use of 2.5 mg and 5 mg has been shown to significantly improve erectile dysfunction in men, including diabetic patients 4, 6
• Long-term safety: Well tolerated for up to 2 years of continuous use 5

Special Populations and Considerations

Renal Impairment

• Moderate impairment (CrCl 30-50 mL/min):
  • As-needed: Start with 5 mg, maximum 10 mg not more than once every 48 hours 1
  • Once-daily: Start with 2.5 mg, may increase to 5 mg based on response 1
• Severe impairment (CrCl <30 mL/min) or hemodialysis:
  • As-needed: Maximum 5 mg not more than once every 72 hours 1
  • Once-daily: Not recommended 1

Hepatic Impairment

• Mild to moderate impairment (Child-Pugh Class A or B):
  • As-needed: Should not exceed 10 mg once per day 1
  • Once-daily: Use with caution 1
• Severe impairment (Child-Pugh Class C): Not recommended 1

Concomitant Medications

• Absolute contraindication: Nitrates (risk of severe hypotension) 4, 7
• CYP3A4 inhibitors: Start with lowest possible dose and monitor for hypotension 7
• Alpha-blockers: Start with lowest recommended dose and ensure patient is stable on alpha-blocker therapy first 7

Clinical Pearls and Pitfalls

• Patients with diabetes or post-prostatectomy may have more severe ED at baseline and respond less robustly to PDE5 inhibitors 4
• Tadalafil may be taken without regard to food 1
• For patients who fail to respond to one PDE5 inhibitor, switching to another (sildenafil, vardenafil, or avanafil) may be effective 7
• Daily use of tadalafil may be beneficial for patients who prefer spontaneous rather than scheduled sexual activity 4
• Some patients who do not achieve normal erectile function with as-needed PDE5 inhibitors may benefit from switching to once-daily tadalafil 8
• If tadalafil is ineffective after proper use at maximum dose on at least 5 separate occasions, consider second-line options such as intracavernosal injections of alprostadil 7

By following these dosing recommendations and considering individual patient factors, tadalafil can be an effective treatment option for erectile dysfunction with both as-needed and once-daily dosing regimens.