ED increases with age from ~35% of men aged 60 to ~50% of men older than 70 being affected. It is a complicated interaction between the aetiology of vascular, neurogenic, hormonal, psychogenic, iatrogenic and anatomic causes, which plays an important role in the occurrence of ED.
Sildenafil and vardenafil are similar in action, with a peak absorption of 30-60 minutes and a half-life of three to five hours. These medications should be taken on an empty stomach to maximise absorption.
Avanafil is absorbed in 20–30 minutes with a half-life of six hours. Tadalafil is a selective PDE5 inhibitor with a half-life of 17.5 hours, which is longer than other available PDE5 inhibitors. This provides a wide window in which to engage in sexual intercourse. It also allows ED patients to choose once-a-day dosing regimen as an alternative to the conventional on-demand dosing regimen. Additionally, it is not affected by food, so it does not have to be taken on an empty stomach.
Currently, tadalafil is the only oral ED medication approved for daily use, rather than on an as-needed basis. Additionally, it has been shown to improve lower urinary tract symptoms in patients with benign prostatic hyperplasia. A systematic review and quantitative meta-analysis integrated the data from randomised controlled trials (RCTs) that compared the efficacy and safety of different dosing regimens of tadalafil. Peng et al (2017) compare the efficacy and safety between tadalafil once-a-day and tadalafil on-demand dosing regimen in patients with ED.
Materials and Methods: A systematic search of Medline, Embase, and Cochrane Library was performed to identify all randomised controlled trials (RCTs) that compared tadalafil used once-a-day with an on-demand dosing regimen for erectile dysfunction. A secondary hand-search was performed in relevant journals, references and the grey literature.
Results: Six RCTs involving a total of 1 534 patients were included in this review. All studies reported the International Index of Erectile Function-Erectile Function domain score, and the results of the meta-analysis showed no difference between the groups. The overall pooled estimated weighted mean differences (WMD) were 0.97 (95% CI -0.37 to 2.32; p = 0.16). Meta-analyses of Sexual Encounter Profile questions two and three (SEP-2 and SEP-3) showed that the once-a-day dosing regimen was superior to the on-demand regimen with statistical significance. The WMD of SEP-2 and SEP-3 were 10.32 (95% CI 3.16-17.48; p = 0.005) and 11.07 (95% CI 2.57-19.56; p = 0.01), respectively. Both dosing regimens of tadalafil showed similar complication rates. The meta-analyses of adverse events showed no significant differences.
Conclusions: The efficacy rates of tadalafil once-a-day and on-demand were similar. No significant difference in safety was found between the two dose regimens of tadalafil.
Krzastek SC, Bopp J, Smith RP, and Kovac R. Recent advances in the understanding and management of erectile dysfunction. F1000Research, 2019.
Peng Z, Yang L, Dong Q, et al. Efficacy and Safety of Tadalafil Once-a-Day versus Tadalafil On-Demand in Patients with Erectile Dysfunction: A Systematic Review and Meta-Analyses. Urol Int 2017; 99:343-352. doi: 10.1159/000477496.