What It Is: A phosphodiesterase (PDE) inhibitor
What It's Approved to Treat: Erectile dysfunction in men or to improve the ability to exercise in adults with pulmonary arterial hypertension
Common Off-label Uses: Enhancing sexual performance in people not diagnosed with erectile dysfunction, improving sexual function in women taking certain antidepressants
CNN called it "the little blue pill that could," and Viagra has certainly made a name for itself over the last two decades. In 1989, Pfizer scientists introduced a drug called sildenafil citrate that they anticipated would help treat high blood pressure and a type of chest pain associated with coronary heart disease called angina. During the drug's clinical trials, volunteers began reporting increased erections several days after taking a dose, and in 1998, the FDA approved the use of Viagra to treat erectile dysfunction [source: Wilson].
A decade later, scientists began finding evidence that the little blue pill could potentially help some women experiencing sexual dysfunction, too. Between 30 to 70 percent of people taking antidepressants experience sexual dysfunction, and a Pfizer-funded study found that seven out of nine women on antidepressants who had problems achieving orgasm recovered when they took Viagra [source: Carollo].
Female sexual response is complicated, and the FDA hasn't approved Viagra for this use in women, but another prescription medication called flibanserin (Addyi), originally developed as an antidepressant, is FDA-approved to treat low sexual desire in premenopausal women [source: Tobah].