- What is sildenafil, and how does it work (mechanism of action)?
- What brand names are available for sildenafil?
- Is sildenafil available as a generic drug?
- Do I need a prescription for sildenafil?
- What are the side effects of sildenafil?
- What is the dosage for sildenafil?
- Which drugs or supplements interact with sildenafil?
- Is sildenafil safe to take if I'm pregnant or breastfeeding?
- What else should I know about sildenafil?
What is sildenafil, and how does it work (mechanism of action)?
Viagra (sildenafil) is an oral drug that is used for treating impotence (or erectile disfunction, ED, the inability to attain or maintain a penile erection). It is in a class of drugs called phosphodiesterase inhibitors (PDE-5 inhibitors) that also includes
It has been estimated that impotence affects 140 million men worldwide. Over half of all men with impotence are thought to have some physical (medical) cause. The remainder are believed to have psychogenic causes of impotence. Medical causes of impotence include diabetes and circulatory, neurological, or urological conditions.
Penile erection is caused by the engorgement of the penis with blood. This engorgement occurs when the blood vessels delivering blood to the penis increase the delivery of blood and the blood vessels carrying blood away from the penis decrease the removal of blood. Under normal conditions, sexual stimulation leads to the production and release of nitric oxide in the penis. Nitric oxide then activates the enzyme, guanylate cyclase, which causes the production of cyclic guanosine monophosphate (cGMP). It is the cGMP that is primarily responsible for the erection by affecting the amount of blood that the blood vessels deliver and remove from the penis.
Viagra inhibits an enzyme called phosphodiesterase-5 (PDE5) which destroys the cGMP. Thus, Viagra prevents the destruction of cGMP and allows cGMP to accumulate and persist longer. The longer cGMP persists, the more prolonged the engorgement of the penis. The FDA approved Viagra in March 1998.
What brand names are available for sildenafil?
Is sildenafil available as a generic drug?
Do I need a prescription for sildenafil?
What are the side effects of sildenafil?
Approximately 15% of persons taking Viagra experience side effects. The most common side effects are:
- facial flushing (1 in 10),
- headaches (1 in 6),
- stomach pain,
- nasal congestion,
- urinary tract infections (UTIs)
- diarrhea, and
- an inability to differentiate between the colors green and blue.
Quick GuideErectile Dysfunction (ED) Causes and Treatment
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Need help identifying pills and medications?
Use the pill identifier tool on RxList.