What is the recommended dosing for Cialis (tadalafil) when used as needed (prn)?

Tadalafil PRN Dosing Recommendations

The recommended starting dose of tadalafil for use as needed (PRN) in most patients is 10 mg taken prior to anticipated sexual activity, with the dose adjustable between 5-20 mg based on individual efficacy and tolerability. 1

Dosing Guidelines

• The FDA-approved dosing range for tadalafil PRN is 5-20 mg, with a maximum recommended dosing frequency of once per day in most patients 1
• The initial dose should be 10 mg for most patients, which can then be increased to 20 mg or decreased to 5 mg depending on response and side effects 1
• Unlike sildenafil and vardenafil, improvement in erectile function with tadalafil is not significantly dose-dependent between 5-20 mg doses 2
• Tadalafil tablets should be taken whole and not split 1
• Tadalafil may be taken without regard to food 1

Timing Considerations

• Tadalafil PRN can improve erectile function for up to 36 hours following dosing, providing a much longer window of opportunity compared to other PDE5 inhibitors 1
• Clinical studies show that tadalafil can begin working as quickly as 16-30 minutes after dosing, with tadalafil 20 mg showing significant erectogenic effect from 16 minutes onward 3
• Most patients (≥79%) take advantage of tadalafil's extended duration of action by attempting intercourse between 4-36 hours after dosing 4
• Many patients (≥53%) specifically utilize the 12-36 hour window after dosing for sexual activity 4

Special Populations and Dose Adjustments

• For patients with renal impairment:

  • Creatinine clearance 30-50 mL/min: Starting dose of 5 mg not more than once per day, with maximum dose of 10 mg not more than once every 48 hours 1
  • Creatinine clearance <30 mL/min: Maximum dose of 5 mg not more than once every 72 hours 1

• For patients with hepatic impairment:

  • Mild to moderate impairment (Child-Pugh Class A or B): Dose should not exceed 10 mg once per day 1
  • Severe hepatic impairment: Generally not recommended by the American Urological Association 2

Efficacy

• High-quality evidence shows that tadalafil significantly improves erectile function compared to placebo, with 69% of men reporting successful sexual intercourse attempts versus 33% with placebo 5, 2
• For patients who have an incomplete response to PRN PDE5 inhibitors, switching to daily tadalafil (2.5-5 mg) may allow return to normal erectile function in approximately 40% of cases 6

Common Pitfalls and Caveats

• Sexual stimulation is necessary for tadalafil to be effective; incorrect use accounts for a large percentage of treatment failures 2
• Tadalafil is contraindicated in patients taking nitrates due to risk of significant hypotension 2
• Men with diabetes or post-prostatectomy may have more severe ED at baseline and may respond less robustly to PDE5 inhibitors including tadalafil 2
• For men with both ED and testosterone deficiency, combining tadalafil with testosterone therapy may be more effective than tadalafil alone 2