What is the dosing and duration of action for Tadalafil (tadalafil) for erectile dysfunction and benign prostatic hyperplasia (BPH)?

Tadalafil Dosing and Duration of Action

Dosing Regimens

Tadalafil is available in two distinct dosing strategies: as-needed dosing (5-20 mg) taken prior to sexual activity with effects lasting up to 36 hours, or once-daily dosing (2.5-5 mg) for continuous coverage. 1

As-Needed Dosing for Erectile Dysfunction

• Start with 10 mg taken prior to anticipated sexual activity 1
• Titrate to 20 mg for improved tolerability or decrease to 5 mg based on individual response 1
• Maximum dosing frequency is once per day 1
• Unlike sildenafil and vardenafil, tadalafil does NOT show dose-dependent improvement between 5 mg, 10 mg, and 20 mg—meaning the choice between doses should be based on tolerability rather than expecting dramatically better efficacy at higher doses 2, 3

Once-Daily Dosing for Erectile Dysfunction

• Start with 2.5 mg taken at approximately the same time every day, without regard to timing of sexual activity 1
• May increase to 5 mg based on individual efficacy and tolerability 1
• This eliminates the need to time medication with sexual activity, providing an alternative for couples who prefer spontaneous rather than scheduled sexual encounters 3

Once-Daily Dosing for BPH or Combined ED/BPH

• Use 5 mg taken at approximately the same time every day 1
• This single dose treats both conditions simultaneously when both are present 3, 4, 5
• When initiating BPH treatment with tadalafil plus finasteride, continue for up to 26 weeks (incremental benefit beyond 26 weeks is unknown) 1

Duration of Action

Tadalafil improves erectile function for up to 36 hours following a single as-needed dose, which is substantially longer than other PDE5 inhibitors 1. This extended window allows for greater spontaneity in sexual activity timing.

Dose Adjustments for Special Populations

Renal Impairment (As-Needed Dosing)

• CrCl 30-50 mL/min: Start with 5 mg, maximum 10 mg once every 48 hours 1
• CrCl <30 mL/min or hemodialysis: Maximum 5 mg once every 72 hours 1

Renal Impairment (Once-Daily Dosing)

• CrCl 30-50 mL/min (for BPH or ED/BPH): Start with 2.5 mg, may increase to 5 mg 1
• CrCl <30 mL/min or hemodialysis: Once-daily dosing is NOT recommended 1

Hepatic Impairment

• Mild to moderate (Child-Pugh A or B): Maximum 10 mg once per day for as-needed dosing; use caution with once-daily dosing 1
• Severe (Child-Pugh C): Tadalafil is NOT recommended 3, 1

Critical Safety Considerations

Absolute Contraindications

Tadalafil is absolutely contraindicated with any form of nitrate use due to risk of potentially fatal hypotension 3, 1. Patients must be explicitly asked about all forms of nitrate use before prescribing 3.

Emergency Nitrate Protocol

If a patient on tadalafil requires emergency nitrate administration, wait 48 hours after the last tadalafil dose before giving nitrates (compared to 24 hours for sildenafil), under close medical supervision 3.

Alpha-Blocker Coadministration

• Patients should be stable on alpha-blocker therapy before initiating tadalafil 1
• Start tadalafil at the lowest recommended dose when coadministering with alpha-blockers 1
• Combination of tadalafil with alpha-blockers for BPH offers no advantage over either agent alone 3

Efficacy Outcomes

High-quality evidence shows 69% of men using tadalafil as-needed report successful sexual intercourse attempts compared to 33% with placebo 2, 3. This efficacy is maintained across various comorbid conditions including diabetes, cardiovascular disease, post-prostatectomy status, depression, and renal failure 2.

For BPH symptoms, tadalafil 5 mg once daily significantly improves International Prostate Symptom Score (IPSS) from baseline, with improvements evident as early as 2 weeks and maintained through 12 weeks 4, 6.

Common Pitfalls and How to Avoid Them

Inadequate Trial Before Declaring Failure

An adequate trial consists of at least 5 separate attempts at maximum dose before declaring treatment failure 3. Many apparent failures result from:

• Lack of sexual stimulation (sexual stimulation is necessary for tadalafil to be effective) 3, 7
• Improper timing or inadequate dosing frequency 3
• Taking medication with a large meal 7
• Unaddressed hormonal abnormalities or relationship issues 3

Special Population Considerations

Men with diabetes and post-prostatectomy patients have more severe ED at baseline and may respond less robustly to PDE5 inhibitors, though tadalafil remains effective in these populations 3. For men with both ED and testosterone deficiency, combining tadalafil with testosterone therapy may be more effective than tadalafil alone 3.

Administration Details

• Tadalafil may be taken without regard to food 1
• Do not split tablets; the entire dose should be taken 1
• Tadalafil has lower rates of flushing compared to other PDE5 inhibitors 3
• Most common adverse events include dyspepsia, headache, back pain, nasal congestion, and myalgia 3