Source: Choi H, et al. Int J Impot Res 2014;27:33-37.

Although the incidence of erectile dysfunction (ED) and lower urinary tract symptoms (LUTS) both increase with age, there is an as-yet ill-explained independent association of LUTS with ED. That is, within each age decile, more severe LUTS is associated with more severe ED.

The PDE-5 inhibitor tadalafil is approved for treatment of LUTS or ED. The dose used to treat LUTS is less than the usually effective dose for ED, but men treating LUTS with low-dose tadalafil (5 mg daily) also report improvements in sexual function.

Tadalfil has the longest half-life of currently available PDE5 inhibitors: 18.5 hours. Based on this long half-life, might tadalafil provide similar symptom improvement in LUTS and ED if provided every other day?

Choi et al performed a trial in men (n = 144) with symptom scores consistent with LUTS and ED to compare 5 mg tadalafil daily vs every other day. LUTS symptoms and sexual dysfunction symptoms improved to a similar degree with both regimens. Although there were some differences in outcomes that were statistically significant in favor of the daily regimen, differences were generally small and of doubtful clinical significance. Men may achieve comparable symptom improvement for ED and LUTS using tadalafil 5 mg every other day, as with everyday dosing.