What is the recommended dosage and administration of Cialis (tadalafil) for erectile dysfunction?

Tadalafil Dosing for Erectile Dysfunction

For erectile dysfunction, start with tadalafil 10 mg taken as needed approximately 30 minutes before sexual activity, or alternatively use 2.5 mg once daily if spontaneous sexual activity is preferred. 1

As-Needed Dosing Strategy

The FDA-approved starting dose is 10 mg taken prior to anticipated sexual activity, with dose adjustment to 20 mg or down to 5 mg based on tolerability rather than efficacy. 1 This recommendation is critical because tadalafil does NOT show dose-dependent improvement in erectile function between 5 mg, 10 mg, and 20 mg—meaning higher doses don't necessarily work better, only potentially cause more side effects. 2, 3

Key Timing Considerations

• Tadalafil can produce erectogenic effects as early as 16 minutes after the 20 mg dose, though 30 minutes is more reliable. 4
• The medication remains effective for up to 36 hours after dosing, providing a substantial window for sexual activity. 1
• Maximum dosing frequency is once per day. 1

Adequate Trial Requirements

• Before declaring treatment failure, ensure at least 5 separate attempts at maximum dose (20 mg), as many failures result from inadequate trials, improper timing, or lack of sexual stimulation. 2
• Sexual stimulation is absolutely necessary for tadalafil to work—it enhances nitric oxide-mediated vasodilation but doesn't create erections without arousal. 2

Once-Daily Dosing Alternative

For couples preferring spontaneous rather than scheduled sexual activity, start with tadalafil 2.5 mg once daily, taken at the same time each day without regard to timing of sexual activity. 1 This can be increased to 5 mg daily based on individual response. 1

Advantages of Daily Dosing

• Eliminates the need to plan sexual activity within a specific timeframe. 2, 5
• Maintains therapeutic plasma levels continuously due to tadalafil's 17.5-hour half-life. 6
• Equally effective as as-needed dosing, with 84-85% of patients reporting improved erections on 5-10 mg daily. 6
• Long-term studies demonstrate sustained efficacy and safety for up to 2 years. 7

Special Population Adjustments

Renal Impairment

• Creatinine clearance 30-50 mL/min (as-needed dosing): Start with 5 mg maximum once daily, with maximum dose of 10 mg once every 48 hours. 1
• Creatinine clearance <30 mL/min or hemodialysis (as-needed): Maximum 5 mg once every 72 hours. 1
• For daily dosing with CrCl <30 mL/min: Not recommended. 1
• For daily dosing with CrCl 30-50 mL/min: Start with 2.5 mg daily, may increase to 5 mg. 3, 1

Hepatic Impairment

• Mild to moderate (Child-Pugh A or B): Maximum 10 mg once daily for as-needed dosing; use caution with daily dosing. 1
• Severe hepatic impairment (Child-Pugh C): Tadalafil is not recommended. 2, 1

Diabetes Mellitus

• Men with diabetes have more severe ED at baseline and may respond less robustly to PDE5 inhibitors. 2, 3
• Both 2.5 mg and 5 mg once-daily dosing remain efficacious and well-tolerated in diabetic patients. 5

Critical Safety Screening

Absolute Contraindications

• Any form of nitrate use (oral, sublingual, transdermal, or recreational) creates risk of potentially fatal hypotension and is an absolute contraindication. 2
• If emergency nitrates are needed, wait 24 hours after sildenafil but 48 hours after tadalafil before administering nitrates under close medical supervision. 2

Cardiovascular Risk Assessment

• Most ED patients are low-risk and 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
• Patients unable to perform moderate physical activity or with indeterminate cardiovascular risk require cardiology referral before prescribing. 2

Common Adverse Effects

• The most frequent side effects are dyspepsia, headache, back pain, nasal congestion, and myalgia. 2
• Tadalafil has lower rates of flushing compared to other PDE5 inhibitors. 2
• In long-term daily dosing studies, adverse events occurred in ≥5% included dyspepsia, headache, back pain, and influenza, with only 3.4% discontinuing due to adverse events. 6

Combination Therapy Considerations

• For men with both ED and testosterone deficiency, combining tadalafil with testosterone therapy is more effective than tadalafil alone. 2
• Testosterone therapy alone is not effective monotherapy for ED. 2
• Before switching therapies, evaluate whether hormonal abnormalities, food/drug interactions, timing issues, inadequate sexual stimulation, heavy alcohol use, or relationship issues are limiting response. 2

Administration Details

• Tadalafil may be taken without regard to food. 1
• Do not split tablets; take the entire dose. 1
• For patients with BPH and ED, tadalafil 5 mg daily treats both conditions simultaneously (FDA-approved indication). 2