The term 'male impotence' was made to come out from locked doors by Viagra. Even today Viagra is the most preferred drug for the treatment of Erectile Dysfunction. Viagra changed the way ED was treated in men. It was the first oral treatment for erectile dysfunction in men. Viagra helped in bringing back sexual pleasures and sexual fantasies back into men’s life who thought they were impotent. Viagra has come a long way since its launch. As Viagra has been in the market for so long, side effects of Viagra have become more obvious. The latest of the side effects found by some German scientists is that higher doses of Viagra (sildenafil) may impair the ability to smell, which is possibly related to an increase in nasal congestion. They found that the 100-mg dose caused a drop in smelling or "olfactory" ability, specifically odor discrimination and odor threshold, compared with placebo. The 50-mg dose, by contrast, had no effect on olfactory function. The most worrying side effect is its causing blindness. It is in medical terms called non-arteritic anterior ischemic optic neuropathy (NAION) among patients taking drugs for erectile dysfunction. Out of 43 reported cases, 38 had taken Viagra; four had taken Cialis, and one had taken Levitra. The number of men taking impotence drugs is estimated at more than 25 million, with about 23 million taking Viagra. The potential world market is estimated at 189 million patients. The market for these drugs began to sputter in 2004; six years after FDA approved Viagra. Manufacturers reported $2.4 billion in sales, at least $1 billion below analysts' earlier forecasts. Pfizer attributed Viagra's 11% drop in sales last year largely to competition from newcomers Cialis and Levitra. Analysts cite limited health care coverage for erectile dysfunction drugs and patients' embarrassment about discussing impotence problems with physicians as the primary factors limiting growth. Experts are now looking at Viagra for the treatment of the heart. Research shows how Viagra acts above the belt have put the pill on pharmacy shelves in a repackaged form, to help the sufferers of a devastating heart and lung condition. Pulmonary arterial hypertension delivers its blow mainly to young women, killing about half of those afflicted within five years of diagnosis. The condition, which affects about 100,000 people worldwide, causes tiny blood vessels in the lungs to thicken and narrow, often for no apparent reason. The lung damage puts huge pressure on the heart via the pulmonary artery, the big vessel that shunts blood from the heart to the lungs. Patients suffer from poor oxygenation of their blood, weakness and shortness of breath. They often die from heart failure Viagra (sildenafil citrate) is known for opening up blood vessels and could provide an effective and a cheaper option for the treatment of the heart. Experts say the drug might help a wide variety of more common heart and lung troubles. Researchers are even investigating whether the pill could protect mountaineers from the potentially lethal effect on the heart of high altitude and low oxygen levels. Viagra inhibits a specific enzyme, and this helps to dilate blood vessels in the penis, causing blood to rush in and enhancing an erection. The same enzyme also happens to be prevalent in the lung. Experts suspect that the drug dilates blood vessels in the lung and inhibits the growth of cells that block the blood vessels, enhancing blood flow and putting less pressure on the heart.