How Do Phosphodiesterase-5 Enzyme Inhibitors Work?

Reviewed on 12/6/2021

How do phosphodiesterase-5 enzyme inhibitors work?

Phosphodiesterase-5 enzyme inhibitors are medications used to treat erectile dysfunction, enlarged prostate (benign prostate hyperplasia), and pulmonary arterial hypertension (PAH), a condition of high blood pressure in the arteries that carry deoxygenated blood from the heart to the lungs.

Phosphodiesterase-5 enzyme inhibitors work in the following ways:

  • Relax the smooth muscles in the penis and increase blood flow into the corpus cavernosum, the erectile tissue in the penis.
  • Improve blood flow in the prostate and relieve urinary symptoms associated with an enlarged prostate.
  • Relax the smooth muscles around the pulmonary arteries, which results in arterial dilation and reduced pulmonary blood pressure

Normally, sexual stimulation causes nitrous oxide to be released into the corpus cavernosum, which increases the concentration of a signaling molecule known as cyclic guanosine monophosphate (cGMP). An increase in cGMP levels leads to relaxation of vascular smooth muscles, dilation of blood vessels, and improved blood flow.

The phosphodiesterase-5 enzyme regulates cGMP levels by degrading them. Phosphodiesterase-5 enzyme inhibitors prevent PDE-5 from degrading cGMP, increase its concentration in the tissue, and enhance the muscle relaxation effects of nitrous oxide.

How are phosphodiesterase-5 enzyme inhibitors used?

Phosphodiesterase-5 enzyme inhibitors are administered orally as tablets or suspensions, or as intravenous injections for the treatment of the following conditions:


Orphan designation:


Erectile Dysfunction (ED) Causes and Treatment See Slideshow

What are side effects of phosphodiesterase-5 enzyme inhibitors?

Side effects of phosphodiesterase-5 enzyme inhibitors may include the following:

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

What are names of phosphodiesterase-5 enzyme inhibitor drugs?

Generic and brand names of phosphoesterase-5 enzyme inhibitor drugs include:


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