Tadalafil每日5 mg與按需20 mg治療勃起功能障礙之療效與安全性：
系統性回顧

蕭亞芝¹、陳曉芳¹、鄭如惠²、黃品叡^3,4,5

1李綜合醫療社團法人苑裡李綜合醫院 醫療部 專科護理師小組

2李綜合醫療社團法人苑裡李綜合醫院 護理部

3李綜合醫療社團法人大甲李綜合醫院 外科部 泌尿外科

4國立陽明交通大學 跨領域醫學博士學位學程

5亞洲大學 食品營養與保健生技學系

Efficacy and Safety of Tadalafil 20 mg On-Demand vs. Tadalafil 5 mg Once-Daily for Erectile Dysfunction: A Systematic Review

Ya-Chih Hsiao¹, Hsiao-Fang Chen¹, Ru-Hui Cheng², Pin-Jui Huang^3,4,5

1Division of Nursing Participants, Department of Medical Affairs, Yuanli Lee Hospital

2Nursing Department, Yuanli Lee Hospital

3Division of Urology, Department of Surgery, Dajia Lee Hospital

4Ph.D. Program in Interdisciplinary Medicine, National Yang Ming Chiao Tung University, Taipei

5Department of Food Nutrition and Health Biotechnology, Asia University, Taichung

Introduction:
Erectile dysfunction (ED) is a prevalent condition affecting men worldwide and significantly impacts quality of life and psychological well-being. Phosphodiesterase type 5 inhibitors (PDE5 inhibitors) are the first-line pharmacological treatment for ED, with tadalafil being widely used due to its long half-life and flexible dosing regimens. Tadalafil can be administered either as an on-demand high dose (20 mg) or as a once-daily low dose (5 mg). While both regimens are commonly used in clinical practice, the comparative efficacy and safety between tadalafil 20 mg on-demand and tadalafil 5 mg once-daily remain subjects of ongoing discussion. This systematic review aims to evaluate the efficacy, safety, patient satisfaction, and clinical considerations of these two tadalafil dosing regimens in the treatment of erectile dysfunction.

Materials and Methods:
A systematic literature search was conducted using PubMed, Embase, and Cochrane Library databases for studies published up to 2025. Search terms included “tadalafil,” “erectile dysfunction,” “once daily,” “on demand,” “20 mg,” and “5 mg.” Randomized controlled trials, prospective studies, and comparative studies evaluating tadalafil 20 mg on-demand versus tadalafil 5 mg once-daily were included. Outcomes assessed included International Index of Erectile Function (IIEF-EF) scores, successful intercourse rates (SEP-2 and SEP-3), patient preference, treatment satisfaction, and adverse events. Studies not directly comparing the two regimens or lacking clinical outcome data were excluded.

Results:
A total of relevant studies were included in this review. Both tadalafil 20 mg on-demand and tadalafil 5 mg once-daily significantly improved erectile function compared to baseline. The 20 mg on-demand regimen generally demonstrated greater improvement in IIEF-EF scores and higher successful intercourse rates due to higher peak plasma concentrations. However, tadalafil 5 mg once-daily provided more spontaneous sexual activity, improved endothelial function, and was particularly beneficial for patients with concomitant lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH). Patient preference varied depending on lifestyle, frequency of sexual activity, and tolerance to side effects. The safety profiles of both regimens were similar, with common adverse effects including headache, flushing, dyspepsia, and back pain. Daily dosing was associated with fewer peak-related adverse effects but higher cumulative drug exposure.

Discussion:
The choice between tadalafil 20 mg on-demand and tadalafil 5 mg once-daily should be individualized based on patient lifestyle, frequency of sexual activity, comorbid LUTS, and tolerance to medication. On-demand dosing may be more suitable for patients with less frequent sexual activity who prefer stronger erectile response, while once-daily dosing may be preferable for patients seeking spontaneity, improved endothelial health, and concurrent LUTS management. Long-term adherence and patient satisfaction may be higher with daily dosing in selected populations.

Conclusion:
Both tadalafil 20 mg on-demand and tadalafil 5 mg once-daily are effective and safe treatments for erectile dysfunction. The 20 mg on-demand regimen may provide stronger erectile response, whereas the 5 mg once-daily regimen offers greater spontaneity and additional benefits for LUTS. Treatment selection should be individualized based on patient preference, comorbidities, and lifestyle factors to optimize treatment outcomes and satisfaction.