Yonkenafil (Tunodafil) hydrochloride, a novel phosphodiesterase 5 ( PDE5 ) inhibitor, is effective in reducing cerebral infarction, neurological deficits, edema, and neuronal damage in the infarcted area. Yonkenafil (Tunodafil) hydrochloride may improve cognitive function by modulating neurogenesis and has a potential therapeutic effect on Alzheimer's disease.