Sildenafil, brand-name Viagra, was originally studied for use in treating high blood pressure and angina. Its effects on these conditions were minimal, but it was found to be useful for treating erectile dysfunction. It was patented in 1996 and approved by the U.S. Food and Drug Administration in 1998. It is prescribed for male erectile dysfunction and pulmonary arterial hypertension, a disorder of high blood pressure in the lungs. It is also being used or investigated for pulmonary arterial hypertension in children, jet lag, altitude sickness and female sexual arousal disorders.
Male Sexual Dysfunction
Erectile dysfunction is a common disorder that shows increasing incidence with age. It has many causes, ranging from diseases of the blood vessels such as those associated with arteriosclerosis or diabetes, to psychological factors. Sexual arousal releases nitric oxide from nerve endings that leads to the formation of a chemical messenger called cGMP. This messenger leads to dilation of blood vessels and erection of the penis. Viagra inhibits an enzyme called PDE5 or phosphodiesterase 5 that breaks down cGMP, so more builds up, providing a stronger signal for dilation of blood vessels. Side effects may include headache, indigestion, flushing and blue vision. Viagra may cause dangerously low blood pressure with nitrates such as nitroglycerin.
Pulmonary Arterial Hypertension
As discussed with erectile dysfunction, the mechanism of action of Viagra causes it to dilate blood vessels. In pulmonary arterial hypertension, the blood vessels of the lungs are constricted, decreasing blood flow to the lungs and placing strain on the heart. Viagra increases the diameter of the blood vessels in the lungs, thereby improving capacity, daily functioning and heart performance in patients with symptomatic pulmonary arterial hypertension, as reported in a New England Journal of Medicine article by Galia and Ghofrani, et al.
Female Sexual Dysfunction / Investigational
Viagra has been investigated for use in women with sexual dysfunction, but results have either been mixed or it has shown to be ineffective, as the causes of female sexual disorders appear to be more variable than in men. However, there may be subsets of women in whom the drug is effective, such as those on antidepressants, according to an article in the Journal of the American Medical Association by Nurnberg and Hensley, et al. It is also being investigated for its use in pulmonary arterial hypertension in children, jet lag and altitude sickness.
References
- Mayo Clinic: Sildenafil Oral
- RxList.com: Sildenafil Citrate: Clinical Pharmacology
- "New England Journal of Medicine"; Sildenafil Citrate Therapy for Pulmonary Arterial Hypertension; Galiè, Ghofrani, Torbicki et al.; Nov 2005
- "Journal of the American Medical Association"; Sildenafil Treatment of Women With Antidepressant-Associated Sexual Dysfunction; Nurnberg, Hensley et al.; July 2008
- Prescription Drug Info.com: Sildenafil Details
