What is the recommended dose of Cialis (tadalafil) for a patient with erectile dysfunction, considering potential kidney or liver disease?

Tadalafil Dosing for Erectile Dysfunction

For erectile dysfunction, start with tadalafil 10 mg taken as needed prior to sexual activity, or alternatively 2.5-5 mg once daily for spontaneous sexual activity, with dose adjustments based on tolerability rather than efficacy since tadalafil shows no dose-dependent improvement between 5-20 mg. 1, 2

Standard As-Needed Dosing

• The FDA-approved starting dose is 10 mg taken prior to anticipated sexual activity, which can be increased to 20 mg or decreased to 5 mg based on individual tolerability 1
• Maximum dosing frequency is once per day in most patients 1
• Tadalafil remains effective for up to 36 hours after dosing, allowing for spontaneous sexual activity without precise timing 1, 2
• Unlike sildenafil and vardenafil, tadalafil does NOT show dose-dependent improvement in erectile function between 5 mg, 10 mg, and 20 mg—meaning the choice between doses should be based primarily on tolerability rather than expecting dramatically better efficacy at higher doses 2, 3

Once-Daily Dosing Alternative

• For patients who prefer spontaneous rather than scheduled sexual activity, start with tadalafil 2.5 mg once daily, which may be increased to 5 mg based on tolerability 1, 2
• Daily dosing eliminates the need to time medication with sexual activity entirely 2, 3
• Take at approximately the same time every day, without regard to timing of sexual activity 1
• Daily dosing produces the same level of efficacy as on-demand dosing 4

Renal Impairment Dosing Adjustments

For patients with kidney disease, dose reductions are mandatory to prevent delayed metabolism and adverse effects:

• Creatinine clearance 30-50 mL/min (as-needed dosing): Start with 5 mg maximum once per day, with maximum dose of 10 mg not more than once every 48 hours 1
• Creatinine clearance <30 mL/min or hemodialysis (as-needed dosing): Maximum dose 5 mg not more than once every 72 hours 1
• Creatinine clearance 30-50 mL/min (daily dosing): Start with 2.5 mg daily, may increase to 5 mg based on response 1, 3
• Creatinine clearance <30 mL/min or hemodialysis (daily dosing): Once-daily tadalafil is NOT recommended 1
• Use with caution at least initially at lower doses given the potential for delayed metabolism 4

Hepatic Impairment Dosing Adjustments

For patients with liver disease, dose limitations are critical:

• Mild or moderate hepatic impairment (Child-Pugh Class A or B): Maximum dose 10 mg once per day 1
• Once-daily dosing has not been extensively evaluated in hepatic impairment; use with caution 1
• In severe renal or liver disease, use of PDE5 inhibitors is generally NOT recommended 4
• Despite these restrictions, research shows tadalafil 10 mg can improve erectile function in compensated cirrhosis patients (Child-Pugh 5-10) with acceptable adverse effects 5

Critical Safety Verification Before Prescribing

Before writing any tadalafil prescription, you must verify:

• Patient is NOT taking nitrates in any form—this combination causes potentially fatal hypotension 2, 1
• Patient can perform moderate physical activity (walk 1 mile in 20 minutes or climb 2 flights of stairs without symptoms)—if unable, refer to cardiology first 2
• Low-risk cardiovascular patients can safely receive tadalafil, including those with asymptomatic CAD with <3 risk factors, controlled hypertension, mild stable angina, successful revascularization, uncomplicated past MI, mild valvular disease, and CHF NYHA Class I 2
• High-risk patients should defer treatment: unstable angina, uncontrolled hypertension, recent MI (<2 weeks), NYHA Class III-IV heart failure, or severe valvular disease 2

Defining Treatment Success and Failure

An adequate trial requires at least 5 separate attempts at maximum tolerated dose before declaring treatment failure 2

Before switching therapies, systematically evaluate these common causes of apparent failure:

• Lack of adequate sexual stimulation (required for tadalafil to work) 4, 2
• Medication taken with large meal (though tadalafil can be taken without regard to food) 1
• Heavy alcohol use impairing erectile function 2
• Undiagnosed testosterone deficiency 2
• Relationship issues with partner 2

Dose Titration Strategy

• Work with the patient to find the dose that meets treatment expectations without unacceptable adverse events—this may require titrating initial doses up or down 4
• The most common adverse events are dyspepsia, headache, back pain, nasal congestion, and myalgia 2, 1
• Tadalafil has lower rates of flushing compared to other PDE5 inhibitors 2
• Higher cumulative doses significantly increase risk of headache, dyspepsia, back pain, myalgia, and hypotension 2

Special Population Considerations

• Men with diabetes and post-prostatectomy patients have more severe ED at baseline and respond less robustly to PDE5 inhibitors, though tadalafil remains effective 4, 2, 3
• For men with ED and testosterone deficiency, combining tadalafil with testosterone therapy is more effective than tadalafil alone—testosterone therapy is NOT effective as monotherapy for ED 4, 2
• For patients with both ED and benign prostatic hyperplasia, tadalafil 5 mg once daily is FDA-approved to treat both conditions simultaneously 2, 1

Emergency Nitrate Protocol

If a patient on tadalafil requires emergency nitrate administration, wait 48 hours after the last tadalafil dose before giving nitrates, under close medical supervision with continuous monitoring 2