Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor, similar to sildenafil (Viagra) and vardenafil (Levitra). Tadalis SX 20 works by increasing blood flow to the penis during sexual stimulation, allowing for an erection to occur.As with other medications containing PDE5 inhibitors, Tadalis SX 20 may have potential side effects. https://www.genericday.com/tadalis-sx-20-mg.html