Udenafil is a phosphodiesterase‑5 inhibitor for erectile dysfunction that enhances nitric‑oxide–cGMP signaling to relax corpus cavernosum smooth muscle and improve penile blood flow during sexual stimulation, without affecting libido itself. It features a relatively rapid onset with max around 0.8–1.5 hours and a half‑life of roughly 10–12 hours, supporting both on‑demand and potential once‑daily regimens per clinical studies in diverse ED populations, including diabetes and hypertension cohorts. Evidence indicates efficacy comparable to other PDE5 inhibitors, with typical tolerability and guidance to individualize timing with meals, alcohol, and comorbid cardiovascular considerations.