Levitra is classified as a drug that slows down the enzyme present in the body known as phosphodiesterases. It is a phosphodiesterase type 5 inhibitor (PDE5 inhibitor) that blocks an enzyme called cGMP-specific phosphodiesterase type 5 (PDE5) and helps smooth blood flow in the penis. The effect of Levitra widens the corpora cavernosa (blood vessel) of the penis, which makes erection easier with sexual stimulation.

Levitra is not prescribed to address the underlying cause of erectile dysfunction. Rather it is used to increase the blood flow by blocking the PDE5 enzyme. PDE5 enzymes usually break down a chemical messenger called cyclic GMP, which reduces blood flow. Hence, blocking the PDE5 enzyme increases the blood vessel in the penis, facilitating erection.