Is it safe for a patient to take tadalafil (Cialis) 5mg daily and 20mg as needed for erectile dysfunction (ED)?

This Dosing Regimen is NOT Safe and Should Be Discontinued Immediately

Combining tadalafil 5mg daily with 20mg as-needed creates a dangerous dosing scenario that violates FDA-approved prescribing guidelines and significantly increases the risk of serious adverse events, including severe hypotension. 1

Why This Combination is Contraindicated

The FDA label explicitly states that tadalafil should be dosed either as-needed OR once-daily, but never both simultaneously 1. Here's the critical safety issue:

• Maximum daily dose violation: On days when the patient takes both the 5mg daily dose AND the 20mg as-needed dose, they receive 25mg total—exceeding the FDA-approved maximum single dose of 20mg 1
• Unpredictable drug accumulation: Tadalafil has a 17.5-hour half-life, meaning the 5mg daily dose creates steady-state drug levels that compound with as-needed dosing, leading to unpredictable total drug exposure 1
• Increased adverse event risk: Higher cumulative doses significantly increase the risk of headache, dyspepsia, back pain, myalgia, and most critically, hypotension—especially if the patient uses nitrates emergently 2, 1

Correct Dosing Strategies (Choose ONE)

Option 1: As-Needed Dosing for ED Only

• Start with tadalafil 10mg as-needed, taken prior to anticipated sexual activity 1
• Titrate to 20mg if 10mg is insufficient, or reduce to 5mg if side effects occur 1
• Maximum frequency: once per day 1
• This approach works up to 36 hours after dosing 1

Option 2: Daily Dosing for Spontaneous Activity

• Tadalafil 2.5-5mg once daily eliminates the need to time medication with sexual activity 3, 1
• The European Association of Urology recommends this for couples preferring spontaneous rather than scheduled sexual activity 3
• Importantly, tadalafil efficacy is NOT dose-dependent between 5-20mg, unlike other PDE5 inhibitors 3, 4

Option 3: If Patient Has Both ED and BPH

• Tadalafil 5mg once daily is FDA-approved to treat both conditions simultaneously 1, 5
• This is the ONLY scenario where 5mg daily is appropriate for ED management 6
• The AUA confirms this dual indication with moderate recommendation strength 2

Critical Safety Verification Before Any Prescribing

Before prescribing any tadalafil regimen, you must verify 2, 3:

• No nitrate use (oral, sublingual, transdermal, or recreational)—this is an absolute contraindication due to potentially fatal hypotension 3, 1
• Cardiovascular risk assessment: Most ED patients are low-risk and can safely receive PDE5 inhibitors, but those unable to perform moderate physical activity require cardiology referral before prescribing 3
• Renal function: If creatinine clearance is 30-50 mL/min, start with 5mg as-needed (maximum 10mg every 48 hours) or 2.5mg daily; if <30 mL/min, as-needed dosing maximum is 5mg every 72 hours 1

Common Pitfall to Avoid

The most frequent error is assuming that combining daily and as-needed dosing provides "better coverage"—it does not 6. Instead, it creates:

• Excessive drug exposure without additional efficacy benefit (since tadalafil efficacy plateaus above 5mg) 3, 4
• Increased adverse events, particularly cardiovascular complications 2, 1
• Violation of FDA prescribing guidelines that could expose you to liability 1

Immediate Action Required

Discontinue the current regimen immediately and choose ONE of the three options above based on:

• Whether the patient has BPH symptoms (if yes → 5mg daily) 1, 5
• Whether the patient prefers spontaneous vs. planned sexual activity (spontaneous → 2.5-5mg daily; planned → 10-20mg as-needed) 3, 1
• Renal function and cardiovascular risk status 1

The Princeton III Consensus confirms that PDE5 inhibitors are safe when used correctly, with no new cardiovascular safety concerns in postmarketing surveillance 2. However, this safety profile assumes adherence to approved dosing regimens—not the dangerous combination your patient is currently using.